CN111740188A - High-selectivity balanced band-pass full-frequency common-mode rejection passband internal common-mode absorption filter - Google Patents

High-selectivity balanced band-pass full-frequency common-mode rejection passband internal common-mode absorption filter Download PDF

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CN111740188A
CN111740188A CN202010537607.9A CN202010537607A CN111740188A CN 111740188 A CN111740188 A CN 111740188A CN 202010537607 A CN202010537607 A CN 202010537607A CN 111740188 A CN111740188 A CN 111740188A
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branch
line
filter circuit
filter
resistor
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CN111740188B (en
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吴永乐
张一凡
魏一文
王卫民
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Beijing University of Posts and Telecommunications
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Beijing University of Posts and Telecommunications
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/20—Frequency-selective devices, e.g. filters
    • H01P1/2002—Dielectric waveguide filters
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/04—Fixed joints
    • H01P1/045—Coaxial joints
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/20—Frequency-selective devices, e.g. filters
    • H01P1/201—Filters for transverse electromagnetic waves
    • H01P1/203—Strip line filters

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  • Filters And Equalizers (AREA)

Abstract

The embodiment of the invention provides a common mode absorption filter in a high-selectivity balanced band-pass full-frequency common mode rejection passband, which comprises: the filter comprises a dielectric substrate, two input ports 1, two output ports 2, a first filter circuit structural unit 3, a second filter circuit structural unit 4, four branches and four resistors, wherein the two input ports, the two output ports, the first filter circuit structural unit 3, the second filter circuit structural unit 4, the four branches and the four resistors are arranged on the dielectric substrate, the branches are transmission lines with impedance, the four branches comprise two first branches Z1 and two second branches Z2, and the four resistors comprise two first resistors R1 and two second resistors R2. The application of the balanced filter provided by the embodiment can reduce the reflection of common mode noise on the basis of good filter characteristics.

Description

High-selectivity balanced band-pass full-frequency common-mode rejection passband internal common-mode absorption filter
Technical Field
The invention relates to the technical field of electricity, in particular to a common-mode absorption filter in a high-selectivity balanced band-pass full-frequency common-mode rejection passband.
Background
With the development of communication technology, a fully balanced radio frequency front end in a communication system can better suppress common mode interference. Specifically, the balanced filter in the fully balanced radio frequency front end can exhibit a suppression effect on common mode noise, and effectively suppress common mode interference, so that the overall efficiency and the anti-interference capability of the communication system can be improved.
However, the conventional balance filter reflects the common mode noise when suppressing the common mode noise. Since the balanced filter is a part of the fully balanced rf front-end, the rf front-end is filled with common mode noise, and the fully balanced rf front-end has many devices sensitive to the common mode noise, and the performance of the devices is easily affected by the common mode noise, thereby affecting the communication performance of the fully balanced rf front-end and the communication performance of the communication system. Therefore, a filter having good filtering characteristics and capable of reducing the reflected common mode noise is needed.
Disclosure of Invention
An object of the embodiments of the present invention is to provide a common mode absorption filter in a high-selectivity balanced band-pass full-band common mode rejection passband, so as to have a good filtering characteristic and reduce reflection of common mode noise. The specific technical scheme is as follows:
in a first aspect, an embodiment of the present invention provides a high-selectivity balanced bandpass full-band common-mode rejection passband internal common-mode absorption filter, where the filter includes: the circuit comprises a dielectric substrate, two input ports 1, two output ports 2, a first filter circuit structure unit 3, a second filter circuit structure unit 4, four branches and four resistors, wherein the two input ports, the two output ports, the first filter circuit structure unit 3, the second filter circuit structure unit 4, the four branches and the four resistors are arranged on the dielectric substrate, the branches are transmission lines with impedance, the four branches comprise two first branches Z1 and two second branches Z2, and the four resistors comprise two first resistors R1 and two second resistors R2; wherein,
the input end of the first filter circuit structure unit 3 is connected with each input port 1 and one end of a second branch Z2, the other end of the second branch Z2 is connected with one end of a first resistor R1, and the other end of the first resistor R1 is grounded;
the output end of the first filter circuit structural unit 3 is connected with one end of each first branch Z1 and one end of a second resistor R2, and the other end of the second resistor R2 is grounded;
the input end of the second filter circuit structural unit 4 is connected with the other end of each first branch Z1 and one end of another second resistor R2, and the other end of the another second resistor R2 is grounded;
the output end of the second filter circuit structure unit 4 is connected to each output port 2 and one end of another second branch Z2, the other end of the another second branch Z2 is connected to one end of another first resistor R1, and the other end of the another first resistor R1 is grounded.
In one embodiment of the present invention, the first filter circuit configuration unit 3 includes: two first filter circuit configuration subunits 31 and a third branch Z3; wherein,
the first filter circuit configuration subunit 31 includes: a first coupled line C1 including a line a and a line b, a fourth branch Z4, a fifth branch Z5, and a sixth branch Z6; wherein:
one end of the b line in the first coupled line C1 is connected to one input port 1 and to one end of the one fourth branch Z4, and the other end of the one fourth branch Z4 is connected to one end of one third branch Z3; one end of the fifth branch Z5 is connected to the other end of the third branch Z3, the other end of the fifth branch Z5 is connected to one end of a first branch Z1 and to one end of a line a in the first coupling line C1, the other end of a line a in the first coupling line C1 is connected to the sixth branch Z6, and the other end of the sixth branch Z6 is grounded;
one end of the one third branch Z3 is connected to one end of the one second branch Z2, and the other end of the one third branch Z3 is connected to one end of the one second resistor R2;
the first coupling line C1 in the two first filter circuit configuration subunits 31 is connected to a different input port 1 and the fifth stub Z5 is connected to one end of a different first stub Z1.
In one embodiment of the present invention, the second filter circuit structure unit 4 includes: two second filter circuit configuration subunits 41 and a further third branch Z3; wherein,
the second filter circuit configuration subunit 41 includes: a second coupled line C2 including a line a and a line b, a fourth branch Z4, a fifth branch Z5, and a sixth branch Z6; wherein:
one end of the b line in the second coupling line C2 is connected to one output port 2 and to one end of the other fourth branch Z4, and the other end of the other fourth branch Z4 is connected to one end of the other third branch Z3; one end of the other fifth branch Z5 is connected to the other end of the other third branch Z3, the other end of the other fifth branch Z5 is connected to the other end of the one first branch Z1 and to one end of a line a in the second coupling line C2, the other end of a line a in the second coupling line C2 is connected to one end of the other sixth branch Z6, and the other end of the other sixth branch Z6 is grounded;
one end of the other third branch Z3 is connected with one end of the other second branch Z2, and the other end of the other third branch Z3 is connected with one end of the other second resistor R2;
the second coupling line C2 in the two second filter circuit configuration subunits 41 is connected to a different output port 2 and the fifth branch Z5 is connected to the other end of a different first branch Z1.
In one embodiment of the present invention, the first coupled line C1 and the second coupled line C2 have the same line width, the same slot width, and the same line length.
In an embodiment of the present invention, the characteristic impedance values of the third branch Z3, the fourth branch Z4, the fifth branch Z5 and the sixth branch Z6 are different.
In an embodiment of the present invention, the fourth branch Z4 and the fifth branch Z5 have the same length and the same width, and the third branch Z3, the fourth branch Z4, and the sixth branch Z6 have different lengths and different widths.
In an embodiment of the present invention, the characteristic impedance values of the first branch Z1 and the second branch Z2 are different.
In an embodiment of the present invention, the first branch Z1 and the second branch Z2 have different lengths and widths.
In one embodiment of the present invention, the two input ports 1 have the same port width and the same port length; the two output ports 2 have the same port width and the same port length.
In an embodiment of the present invention, the input port 1 is an SMA connector, and the output port 2 is an SMA connector.
As can be seen from the above, in the filter according to the embodiment of the present invention, one end of the second branch Z2 is connected to one end of the first resistor R1, the other end of the first resistor R1 is grounded, the other end of the second branch Z2 is connected to one end of the second resistor R2 through the circuit structure unit, and the other end of the second resistor R2 is grounded. That is, one end of the first resistor R1 is grounded, the second resistor R2 is grounded, and the first resistor R1 and the second resistor R2 are connected through the second branch Z2. And when the two resistors in the balanced filter are grounded and connected through the branch knots, the balanced filter can suppress the common-mode noise of the full frequency band under the excitation of the common-mode signal and can convert the reflected common-mode noise into heat, so that the common-mode noise is effectively prevented from being reflected to the front end of the fully balanced radio frequency. Therefore, the filter provided by the embodiment of the invention has less common-mode noise reflection and can suppress the common-mode noise of the full frequency band. Therefore, the balance filter provided by the embodiment of the invention can reduce the reflection of common-mode noise on the basis of good filtering characteristics.
Of course, not all of the advantages described above need to be achieved at the same time in the practice of any one product or method of the invention.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a first balanced filter according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a second balanced filter according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a third balanced filter according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a fourth balanced filter according to an embodiment of the present invention;
FIG. 5 is a schematic diagram illustrating dimensions of a dielectric substrate and a metal ground according to an embodiment of the present invention;
fig. 6a is a schematic circuit diagram of a balanced filter according to an embodiment of the present invention;
fig. 6b is a partial schematic diagram of a corner of a coupled line in a balanced filter according to an embodiment of the present invention;
fig. 6c is a partial schematic diagram of a connection between a resistor and a transmission line in a balanced filter according to an embodiment of the present invention;
fig. 6d is a partial schematic diagram of a coupling line and a transmission line connection in a balanced filter according to an embodiment of the present invention;
fig. 7 is a schematic diagram of a simulation result of S parameters of a balance filter under differential mode excitation according to an embodiment of the present invention;
fig. 8 is a schematic diagram of a simulation result of S-parameters of a balanced filter under common-mode excitation according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a first balance filter according to an embodiment of the present invention.
The balance filter is used for receiving the differential mode signal, and under the excitation of the differential mode signal, the balance filter presents a band-pass filtering characteristic, and under the excitation of the common mode signal, the balance filter can show a suppression effect on common mode noise.
The above-mentioned filter includes: the circuit comprises a dielectric substrate, two input ports 1, two output ports 2, a first filter circuit structure unit 3, a second filter circuit structure unit 4, four branches and four resistors, wherein the two input ports, the two output ports, the first filter circuit structure unit, the second filter circuit structure unit, the four branches and the four resistors are arranged on the dielectric substrate.
The branch is a transmission line with impedance. The four branches comprise two first branches Z1 and two second branches Z2. The four resistors include two first resistors R1 and two second resistors R2.
In an embodiment of the present invention, the characteristic impedance values of the first branch Z1 and the second branch Z2 may be different.
In an embodiment of the present invention, the lengths and widths of the first branch Z1 and the second branch Z2 may be different.
In an embodiment of the present invention, the first filter circuit structure unit 3 and the second filter circuit structure unit 4 may be the same. Specifically, the connection relationship between elements included in the first filter circuit configuration unit 3 and the connection relationship between elements included in the second filter circuit configuration unit 4 may be the same.
In one embodiment of the present invention, the dielectric substrate may be TaconicCER-10, the dielectric substrate may have a dielectric constant of 10, a thickness of 1.6mm, and a dielectric loss of 0.0035.
In one embodiment of the present invention, the port widths of the two input ports 1 may be the same, and the port lengths may be the same. The port widths of the two output ports 2 may be the same and the port lengths may be the same.
In an embodiment of the present invention, the input port 1 may be an SMA (SubMiniature version a) connector, and the output port 2 may be an SMA connector.
Specifically, the input terminal of the first filter circuit configuration unit 3 is connected to each of the input port 1 and one end of one second branch Z2, the other end of the one second branch Z2 is connected to one end of one first resistor R1, and the other end of the one first resistor R1 is grounded.
The output terminal of the first filter circuit structure unit 3 is connected to one terminal of each of the first branches Z1 and one terminal of one of the second resistors R2, and the other terminal of the one of the second resistors R2 is grounded.
The input terminal of the second filter circuit structure unit 4 is connected to the other terminal of each first branch Z1 and one terminal of the other second resistor R2, and the other terminal of the other second resistor R2 is grounded.
The output terminal of the second filter circuit structure unit 4 is connected to each of the output ports 2 and one end of the second branch Z2, the other end of the second branch Z2 is connected to one end of the first resistor R1, and the other end of the first resistor R1 is grounded.
One end of the second branch Z2 is connected to one end of a first resistor R1, the other end of the first resistor R1 is grounded, the other end of the second branch Z2 is connected to one end of a second resistor R2 via the circuit configuration unit, and the other end of the second resistor R2 is grounded. That is, one end of the first resistor R1 is grounded, the second resistor R2 is grounded, and the first resistor R1 and the second resistor R2 are connected through the second branch Z2. And when the two resistors in the balanced filter are grounded and connected through the branch joints, the balanced filter can suppress the common-mode noise of the full frequency band under the excitation of the common-mode signal and can convert the common-mode noise reflected by the balanced filter into heat, so that the common-mode noise is effectively prevented from being reflected to the front end of the fully balanced radio frequency. Therefore, the filter provided by the embodiment can suppress the common mode noise of the full frequency band, and the reflected common mode noise is less.
Each filter circuit structure unit is one unit in the circuit structure of the filter, and the filter with better filter characteristics can be obtained after the filter circuit structure units are connected according to the circuit connection mode.
Since the two input ports 1 have a symmetrical structure and the two output ports 2 have a symmetrical structure, the two input ports 1 may be referred to as balanced input ports and the two output ports 2 may be referred to as balanced output ports.
In an embodiment of the present invention, due to the connection relationship among the first resistor R1, the second resistor R2, the first branch Z1, and the second branch Z2, the balance filter can suppress the common mode noise of the full frequency band under the excitation of the common mode signal, and can convert the reflected common mode noise into heat, so as to absorb the common mode noise. Therefore, the values of the first resistor R1, the second resistor R2, the first branch Z1, and the second branch Z2 may be related to the performance constraint value of the balance filter.
As can be seen from the above, in the filter provided in this embodiment, one end of the second branch Z2 is connected to one end of the first resistor R1, the other end of the first resistor R1 is grounded, the other end of the second branch Z2 is connected to one end of the second resistor R2 through the circuit structure unit, and the other end of the second resistor R2 is grounded. That is, one end of the first resistor R1 is grounded, the second resistor R2 is grounded, and the first resistor R1 and the second resistor R2 are connected through the second branch Z2. And when the two resistors in the balanced filter are grounded and connected through the branch knots, the balanced filter can suppress the common-mode noise of the full frequency band under the excitation of the common-mode signal and can convert the reflected common-mode noise into heat, so that the common-mode noise is effectively prevented from being reflected to the front end of the fully balanced radio frequency. Therefore, the filter provided by the embodiment reflects less common mode noise and can suppress the common mode noise of the full frequency band. Therefore, the balance filter provided by the embodiment of the invention can reduce the reflection of common-mode noise on the basis of good filtering characteristics.
Referring to fig. 2, fig. 2 is a schematic structural diagram of a second balanced filter according to an embodiment of the present invention. In addition to the above embodiments, the first filter circuit structure unit 3 may include: two first filter circuit configuration subunits 31 and a third branch Z3.
The first filter circuit configuration subunit 31 includes: a first coupled line C1 comprising a line a and a line b, a fourth branch Z4, a fifth branch Z5, a sixth branch Z6.
Since the first coupled line C1 includes two transmission lines with a short distance, in order to distinguish two lines with a short distance in the first coupled line C1, one line may be used as the a line, and the other line may be used as the b line.
In one embodiment of the present invention, the electrical length of the first coupling line C1 may be 90 °.
In an embodiment of the invention, the characteristic impedance values of the third branch Z3, the fourth branch Z4, the fifth branch Z5 and the sixth branch Z6 may be different.
In an embodiment of the present invention, the lengths of the fourth branch Z4 and the fifth branch Z5 may be the same, and the widths thereof may be the same. The third branch Z3, the fourth branch Z4 and the sixth branch Z6 may have different lengths and different widths.
Specifically, one end of the b-line of the first coupled line C1 is connected to one input port 1 and one end of the fourth branch Z4.
The other end of the above-mentioned one fourth branch Z4 is connected to one end of one third branch Z3.
One end of the one fifth branch Z5 is connected to the other end of the one third branch Z3, and the other end of the one fifth branch Z5 is connected to one end of the one first branch Z1 and to one end of the a-line of the first coupled line C1.
The other end of the a-line of the first coupled line C1 is connected to the sixth branch Z6, and the other end of the sixth branch Z6 is grounded.
One end of the one third branch Z3 is connected to one end of the one second branch Z2, and the other end of the one third branch Z3 is connected to one end of the one second resistor R2.
The first coupling lines C1 in the two first filter circuit structure subunits 31 are connected to different input ports 1, and the fifth branch Z5 is connected to one end of a different first branch Z1.
Since the first filter circuit structure unit 3 includes the first coupling line C1, and the other end of the a line of the first coupling line C1 is connected to the sixth branch Z6, and the other end of the sixth branch Z6 is grounded. And because the input port in the filter is connected with the coupling line, and one of the coupling lines is connected with one grounding branch, the filter bandwidth can be widened, and the transmission pole is increased, so that the filter has wider filter bandwidth and high selectivity. Therefore, the filter provided by the embodiment has a wider filtering bandwidth and high selectivity.
In one embodiment of the present invention, the connection relationship between the first coupling line C1 and the sixth branch Z6 enables the filter to have a wider filtering bandwidth and high selectivity. Therefore, the parameter values of the first coupling line C1 and the sixth branch Z6 may be related to the performance constraint value of the filter.
Referring to fig. 3, fig. 3 is a schematic structural diagram of a third balanced filter according to an embodiment of the present invention. In the above embodiment, the second filter circuit configuration unit 4 includes: two second filter circuit configuration subunits 41 and a further third branch Z3;
the second filter circuit configuration subunit 41 includes: a second coupled line C2 comprising a line a and a line b, another fourth branch Z4, another fifth branch Z5, another sixth branch Z6.
Since the second coupled line C2 includes two transmission lines with a short distance, in order to distinguish two lines with a short distance in the second coupled line C2, one line may be used as the a line, and the other line may be used as the b line.
In an embodiment of the present invention, the electrical length of the second coupling line C2 may be 90 °.
In an embodiment of the invention, the characteristic impedance values of the third branch Z3, the fourth branch Z4, the fifth branch Z5 and the sixth branch Z6 may be different.
In an embodiment of the present invention, the lengths of the fourth branch Z4 and the fifth branch Z5 may be the same, and the widths thereof may be the same. The lengths and widths of the third branch Z3, the fourth branch Z4 and the sixth branch Z6 may be different.
Specifically, one end of the b-line in the second coupling line C2 is connected to one output port 2, and is connected to one end of the fourth branch Z4.
The other end of the other fourth branch Z4 is connected to one end of the other third branch Z3.
One end of the fifth branch Z5 is connected to the other end of the third branch Z3, and the other end of the fifth branch Z5 is connected to the other end of the first branch Z1 and to one end of the a-line of the second coupled line C2.
The other end of the a line of the second coupling line C2 is connected to one end of another sixth branch Z6.
The other end of the sixth branch Z6 is grounded.
One end of the third branch Z3 is connected to one end of the second branch Z2, and the other end of the third branch Z3 is connected to one end of the second resistor R2.
The second coupling lines C2 in the two second filter circuit structure subunits 41 are connected to different output ports 2, and the fifth branch Z5 is connected to the other end of the different first branch Z1.
Since the second filter circuit structure unit 4 includes the second coupling line C2, the other end of the a line of the second coupling line C2 is connected to the sixth branch Z6, and the other end of the sixth branch Z6 is grounded. And because the output port in the filter is connected with the coupling line, and one line in the coupling line is connected with one grounding branch, the filtering bandwidth can be widened, and the transmission pole is increased, so that the filtering bandwidth of the filter is wider and has high selectivity. Therefore, the filter provided by the embodiment has a wider filtering bandwidth and high selectivity.
In an embodiment of the invention, due to the connection relationship between the second coupling line C2 and the sixth branch Z6, the filter has a wider filtering bandwidth and high selectivity. Therefore, the parameter values of the second coupling line C2 and the sixth branch Z6 may be related to the performance constraint value of the filter.
In an embodiment of the present invention, the filter may be constructed on a single-layer circuit board, and specifically, may be constructed by using a design method of a single-layer printed circuit board. The top layer of the circuit board is a filter circuit structure, and the bottom layer is a metal grounding surface.
Therefore, the constructed filter has a simple integral structure, is easy to process and integrate, and has a novel design idea.
Referring to fig. 4, fig. 4 is a schematic structural diagram of a fourth balanced filter according to an embodiment of the present invention. Fig. 4 includes: the circuit comprises two input ports 1, two output ports 2, a first filter circuit structure unit 3, a second filter circuit structure unit 4, four branches and four resistors.
The four branches comprise two first branches Z1 and two second branches Z2.
The four resistors comprise two first resistors R1 and two second resistors R2.
Specifically, the input terminal of the first filter circuit configuration unit 3 is connected to each of the input port 1 and one end of one second branch Z2, the other end of the one second branch Z2 is connected to one end of one first resistor R1, and the other end of the one first resistor R1 is grounded.
The output terminal of the first filter circuit structure unit 3 is connected to one terminal of each of the first branches Z1 and one terminal of one of the second resistors R2, and the other terminal of the one of the second resistors R2 is grounded.
The input terminal of the second filter circuit structure unit 4 is connected to the other terminal of each first branch Z1 and one terminal of the other second resistor R2, and the other terminal of the other second resistor R2 is grounded.
The output terminal of the second filter circuit structure unit 4 is connected to each of the output ports 2 and one end of the second branch Z2, the other end of the second branch Z2 is connected to one end of the first resistor R1, and the other end of the first resistor R1 is grounded.
Specifically, the first filter circuit configuration unit 3 includes: two first filter circuit configuration subunits 31 and a third branch Z3.
The first filter circuit configuration subunit 31 includes: a first coupled line C1 comprising a line a and a line b, a fourth branch Z4, a fifth branch Z5, a sixth branch Z6.
One end of the b-line of the first coupled line C1 is connected to one input port 1 and one end of a fourth branch Z4.
The other end of the above-mentioned one fourth branch Z4 is connected to one end of one third branch Z3.
One end of the one fifth branch Z5 is connected to the other end of the one third branch Z3, and the other end of the one fifth branch Z5 is connected to one end of the one first branch Z1 and to one end of the a-line of the first coupled line C1.
The other end of the a-line of the first coupled line C1 is connected to the sixth branch Z6, and the other end of the sixth branch Z6 is grounded.
One end of the one third branch Z3 is connected to one end of the one second branch Z2, and the other end of the one third branch Z3 is connected to one end of the one second resistor R2.
The first coupling lines C1 in the two first filter circuit structure subunits 31 are connected to different input ports 1, and the fifth branch Z5 is connected to one end of a different first branch Z1.
Specifically, the second filter circuit structure unit 4 includes: two second filter circuit configuration subunits 41 and a further third branch Z3;
the second filter circuit configuration subunit 41 includes: a second coupled line C2 comprising a line a and a line b, another fourth branch Z4, another fifth branch Z5, another sixth branch Z6.
One end of the b-line of the second coupling line C2 is connected to one output port 2 and to one end of the other fourth branch Z4.
The other end of the other fourth branch Z4 is connected to one end of the other third branch Z3.
One end of the fifth branch Z5 is connected to the other end of the third branch Z3, and the other end of the fifth branch Z5 is connected to the other end of the first branch Z1 and to one end of the a-line of the second coupled line C2.
The other end of the a-line of the second coupling line C2 is connected to one end of another sixth branch Z6, and the other end of the sixth branch Z6 is grounded.
One end of the third branch Z3 is connected to one end of the second branch Z2, and the other end of the third branch Z3 is connected to one end of the second resistor R2.
The second coupling lines C2 in the two second filter circuit structure subunits 41 are connected to different output ports 2, and the fifth branch Z5 is connected to the other end of the different first branch Z1.
As can be seen from the above description, the balanced filter provided in this embodiment is a filter having a symmetrical structure, because each element and connection relationship in the balanced filter are symmetrical up, down, left and right.
Referring to fig. 5, fig. 5 is a schematic size diagram of a dielectric substrate and a metal ground according to an embodiment of the present invention. As can be seen from fig. 5, the metal ground and the dielectric substrate are uniform in size.
Specifically, L in FIG. 5aDenotes the lateral width of the metal ground and the dielectric substrate, and Wa denotes the longitudinal width of the metal ground and the dielectric substrate. WbTransversely digging out the depth L of four corners of the metal ground and the medium substrate, namely the upper left corner, the lower left corner, the upper right corner and the lower right cornerbAnd the depth of the metal ground and four corners of the medium substrate, namely the upper left corner, the lower left corner, the upper right corner and the lower right corner, is dug longitudinally.
In the figure, L is as defined aboveaCan be 55.8mm, WaCan be 29mm, LbMay be 7.75mm, WbMay be 6.5 mm.
The dielectric substrate is very small in size, and the circuit structure on the dielectric substrate is simple, so that the dielectric substrate is easy to process and integrate, and the circuit structure is planar, so that the dielectric substrate can be widely applied to a full-balanced radio frequency front end.
Referring to fig. 6a, fig. 6a is a schematic circuit structure diagram of a balanced filter according to an embodiment of the present invention.
The trapezoid frames at the upper left corner and the lower left corner of fig. 6a are input ports, respectively, and the trapezoid frames at the upper right corner and the lower right corner are output ports, respectively. Where Wp is the width of the input port and the output port, and Lp is the length of the input port and the output port. Specifically, Wp may be 1.5mm, and Lp may be 8.2 mm.
In fig. 6a, two transmission lines with similar distances are arranged at adjacent positions on the right side of the trapezoid frame at the upper left corner and the lower left corner, and the two transmission lines with similar distances are coupling lines. Two transmission lines with similar distances are arranged at the adjacent positions on the left side of the trapezoid frame at the upper right corner and the lower right corner, and the two transmission lines with similar distances are coupling lines. Wherein, WeFor the line width of the coupled line, SeLe is the thread of the coupled line for the slot width of the coupled line. The line width, the slit width and the line length of the four coupling lines are equal, specifically, We may be 0.1mm, and S iseMay be 0.15mm, L aboveeMay be 9 mm.
The transmission line connected to the input port or the output port among the coupled lines is a line b, and the transmission line not connected to the input port or the output port among the coupled lines is a line a. Thus, in the upper half of fig. 6a, the upper transmission line of the coupled lines is the a-line and the lower transmission line of the coupled lines is the b-line; the lower transmission line of the coupled lines is a b-line. In the lower half of fig. 6a, the lower one of the coupled lines is the a-line and the upper one of the coupled lines is the b-line. In fig. 6a, the circular frame closer to the line a is a grounding hole, specifically, the line a is grounded through a short-circuit line, (L)s1+Ls2) Ws is the width of the short-circuited line. Specifically, the above(Ls1+Ls2) The thickness may be 8.6mm, and the Ws may be 0.1 mm.
In the upper half of fig. 6a, the right end of the a-line in the left coupled line is connected with the left end of the a-line in the right coupled line through a horizontal transmission line. In the lower half of fig. 6a, the right end of the a-line in the left coupled line is connected to the left end of the a-line in the right coupled line by a horizontal transmission line. Wherein L is3The length of the transmission line, W3The width of the transmission line. The two transmission lines have the same length and width. Specifically, L3May be 8mm, W3May be 0.1 mm.
In the left half of fig. 6a, the line a in the upper coupled line and the line a in the lower coupled line are connected by two transmission lines in the vertical direction. In the right half of fig. 6a, the a-line in the upper coupled line and the a-line in the lower coupled line are connected by two transmission lines in the vertical direction. Wherein L is2For the length of each of the two transmission lines, W2The width of each of the two transmission lines is described above. Specifically, L2Can be 9.5mm, W2May be 0.4 mm.
In the left half of fig. 6a, the two ladder frames are connected by two transmission lines, and in the right half of fig. 6b, the two ladder frames are connected by two transmission lines. Wherein L is1For the length of each of the two transmission lines, W1The width of each of the two transmission lines is described above. Specifically, L1Can be 9.5mm, W1May be 0.4 mm.
In fig. 6a, there are four rectangular frames, and each rectangular frame has three circles inside, and the circle inside each rectangular frame is a ground hole. Resistance R1Resistor R connected to the middle vertical rectangular frame of FIG. 6a2Connected with the rectangular frames in the horizontal direction at both sides of fig. 6 a. The above resistance R1Resistance R2Are equal in length, wherein,S1is a resistance R1Resistance R2Length of (d).
Resistor R in FIG. 6a1And a resistor R2Connected by two transmission lines, wherein L4Is a length of a transmission lineDegree, W4The width of the transmission line. L istThe length of another transmission line, Wt is the width of the above another transmission line. Specifically, the above-mentioned L4Can be 7mm, W4Can be 0.1mm, W4Can be 7.4mm, LtMay be 0.4 mm.
The upper dashed box in fig. 6a corresponds to fig. 6b, the middle dashed box in fig. 6b corresponds to fig. 6c, and the lower dashed box in fig. 6a corresponds to fig. 6 d.
Referring to fig. 6b, fig. 6b is a partial schematic diagram of a corner of a coupled line in a balanced filter according to an embodiment of the present invention.
In fig. 6b, the left rectangular frame is an input port, and two adjacent transmission lines with a small distance on the right side of the rectangular frame are coupled lines. The transmission line connected with the rectangular frame in the coupling line is a line b, and the transmission line not connected with the rectangular frame in the coupling line is a line a. A square frame is arranged above the line A, a circle is arranged in the square frame, and the circle is a grounding hole. The a line is grounded through a short circuit line (L)s1+Ls2) Ws is the width of the short-circuited line. Specifically, the above (L)s1+Ls2) The thickness may be 8.6mm, and the Ws may be 0.1 mm. Wp is the width of the input port, which may be 1.5 mm.
Referring to fig. 6c, fig. 6c is a partial schematic diagram of a connection between a resistor and a transmission line in a balanced filter according to an embodiment of the present invention.
The circles in the left and right rectangular frames in FIG. 6c are grounding holes, the resistor R1 is connected with the left rectangular frame, the resistor R2 is connected with the right rectangular frame, and the resistor R1And a resistor R2Are connected by two transmission lines, LtLength of transmission line on left side, W4The width of the right transmission line. S1Is a resistance R1Resistance R2Length of (d). Specifically, the above-mentioned W4May be 0.1mm, LtMay be 0.4 mm.
Referring to fig. 6d, fig. 6d is a partial schematic diagram of a coupling line and a transmission line connection in a balanced filter according to an embodiment of the present invention.
In fig. 6d, two lines closer to the left are coupling lines, the rectangular frame is a ground hole, a line connected to the ground hole in the coupling lines is a line, and a line not connected to the ground hole in the coupling lines is b line, where W is WeFor the line width of the coupled line, SeFor the width of the slot of the coupled line, L3Is the length of the transmission line connected to the a-line. In particular, We may be 0.1mm, S as described aboveeMay be 0.15mm, L3May be 8 mm.
Referring to fig. 7, fig. 7 is a schematic diagram of a simulation result of S parameters of a balanced filter under differential mode excitation according to an embodiment of the present invention. In fig. 7, the abscissa is frequency in GHz, and the ordinate is S parameter value in units of: dB.
As can be seen from FIG. 7, at a frequency of 3.5GHz, the insertion loss Sdd21 is-0.4 dB, the range of the insertion loss Sdd21 greater than-3 dB is 2.11GHz to 4.80GHz, the 3dB bandwidth is 2.69GHz, and the 3dB relative bandwidth is 76.86%. The filter can achieve broadband filtering performance and achieve smaller insertion loss.
At a frequency of 3.5GHz, the return loss Sdd11 is-16.18 dB, the range of the return loss Sdd11 smaller than-15 dB is 2.58GHz to 4.72GHz, the bandwidth is 2.14GHz, the relative bandwidth is 61.15%, the range of the return loss Sdd11 smaller than-10 dB is 2.47GHz to 4.75GHz, the bandwidth is 2.28GHz, and the relative bandwidth is 65.15%.
The four reflection zero points are respectively positioned at 2.76GHz, 3.96GHz, 4.38GHz and 4.64GHz, the return loss Sdd11 at the reflection zero points are respectively-37.58 dB, -39.02dB, -41.12dB and-36.20 dB, and the existence of the reflection zero points realizes the high selectivity of the filtering performance of the balanced band-pass filter under the differential mode excitation. Meanwhile, the filter has wider relative bandwidth, and can realize better broadband differential mode response.
Referring to fig. 8, fig. 8 is a schematic diagram of a simulation result of S parameters of a balanced filter under common-mode excitation according to an embodiment of the present invention. In fig. 8, the abscissa is frequency in GHz, and the ordinate is S parameter value in units of: dB.
It can be seen from fig. 8 that the insertion loss Scc21 is-27.89 dB at the frequency of 3.5GHz, and the insertion loss Scc21 is-54.22 dB at 3.7GHz, which can achieve deep rejection of common mode noise.
In the frequency range of 0-8GHz, the insertion loss Scc21 is smaller than-14.58 dB, so that the suppression effect on common mode noise in the full frequency band range can be realized, and the transmission of the common mode noise in the full frequency band range can be effectively suppressed.
When the frequency is 3.5GHz, the return loss Scc11 is-45 dB, the range of the return loss Scc11 smaller than-10 dB is 2.32GHz to 4.43GHz, the bandwidth is 2.11GHz, the relative bandwidth is 60.3%, the range of the return loss Scc11 smaller than-15 dB is 3.08GHz to 4.16GHz, and the relative bandwidth is 30.86%. At 3.72GHz, the return loss Scc11 is-54.67 dB, and effective absorption of common mode noise can be realized. The reflected common mode noise is converted into heat by introducing the grounding resistor, so that the common mode noise can be effectively prevented from being reflected into a balance system to influence the performance of other microwave devices. The 10dB absorption bandwidth of the common mode noise is 60.3%, which shows that the filter can realize broadband common mode noise absorption, and the return loss Scc11 is-54.67 dB at 3.72GHz, which shows that the filter can realize effective absorption of the common mode noise and has a good absorption effect.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims (10)

1. A high selectivity balanced bandpass full-band common-mode rejection passband internal common-mode absorption filter, comprising: the circuit comprises a dielectric substrate, two input ports (1), two output ports (2), a first filter circuit structure unit (3), a second filter circuit structure unit (4), four branches and four resistors, wherein the two input ports, the two output ports, the first filter circuit structure unit (2), the first filter circuit structure unit, the second filter circuit structure unit (4), the four branches and the four resistors are arranged on the dielectric substrate, the branches are transmission lines with impedance, the four branches comprise two first branches (Z1) and two second branches (Z2), and the four resistors comprise two first resistors (R1) and two second resistors (R2); wherein,
the input end of the first filter circuit structure unit (3) is connected with each input port (1) and one end of one second branch (Z2), the other end of the second branch (Z2) is connected with one end of one first resistor (R1), and the other end of the first resistor (R1) is grounded;
the output end of the first filter circuit structure unit (3) is connected with one end of each first branch (Z1) and one end of a second resistor (R2), and the other end of the second resistor (R2) is grounded;
the input end of the second filter circuit structural unit (4) is connected with the other end of each first branch (Z1) and one end of another second resistor (R2), and the other end of the another second resistor (R2) is grounded;
the output end of the second filter circuit structure unit (4) is connected with each output port (2) and one end of another second branch (Z2), the other end of the another second branch (Z2) is connected with one end of another first resistor (R1), and the other end of the another first resistor (R1) is grounded.
2. The filter according to claim 1, characterized in that the first filter circuit configuration unit (3) comprises: two first filter circuit configuration subunits (31) and a third branch (Z3); wherein,
the first filter circuit configuration subunit (31) comprises: a first coupled line (C1) comprising a line a and a line b, a fourth branch (Z4), a fifth branch (Z5) and a sixth branch (Z6); wherein:
one end of the b line in the first coupled line (C1) is connected with one input port (1) and one end of the fourth branch (Z4), and the other end of the fourth branch (Z4) is connected with one end of the third branch (Z3); one end of the fifth branch (Z5) is connected with the other end of the third branch (Z3), the other end of the fifth branch (Z5) is connected with one end of a first branch (Z1) and one end of a line a in the first coupling line (C1), the other end of the line a in the first coupling line (C1) is connected with the sixth branch (Z6), and the other end of the sixth branch (Z6) is grounded;
one end of the one third branch (Z3) is connected to one end of the one second branch (Z2), and the other end of the one third branch (Z3) is connected to one end of the one second resistor (R2);
the first coupling lines (C1) of the two first filter circuit configuration subunits (31) are connected to different input ports (1) and the fifth branch (Z5) is connected to one end of a different first branch (Z1).
3. A filter according to claim 2, characterized in that the second filter circuit configuration unit (4) comprises: two second filter circuit configuration subunits (41) and a further third branch (Z3); wherein,
the second filter circuit configuration subunit (41) comprises: a second coupled line (C2) including a line a and a line b, another fourth branch (Z4), another fifth branch (Z5), another sixth branch (Z6); wherein:
one end of a line b in the second coupling line (C2) is connected with one output port (2) and is connected with one end of the other fourth branch (Z4), and the other end of the other fourth branch (Z4) is connected with one end of the other third branch (Z3); one end of the other fifth branch (Z5) is connected with the other end of the other third branch (Z3), the other end of the other fifth branch (Z5) is connected with the other end of one first branch (Z1) and with one end of a line a in the second coupling line (C2), the other end of a line a in the second coupling line (C2) is connected with one end of the other sixth branch (Z6), and the other end of the other sixth branch (Z6) is grounded;
one end of the other third branch (Z3) is connected with one end of the other second branch (Z2), and the other end of the other third branch (Z3) is connected with one end of the other second resistor (R2);
the second coupling lines (C2) of the two second filter circuit configuration subunits (41) are connected to different output ports (2) and the fifth branch (Z5) is connected to the other end of a different first branch (Z1).
4. A filter according to claim 3, characterised in that the first coupled line (C1) and the second coupled line (C2) have the same line width, the same slot width and the same line length.
5. The filter according to claim 3, characterized in that the values of the characteristic impedance between the third (Z3), the fourth (Z4), the fifth (Z5) and the sixth (Z6) branches are different.
6. The filter according to claim 3, characterized in that the fourth branch (Z4) and the fifth branch (Z5) have the same length and the same width, and the third branch (Z3), the fourth branch (Z4) and the sixth branch (Z6) have different lengths and different widths.
7. The filter according to claim 1, characterized in that the characteristic impedance values between the first branch (Z1) and the second branch (Z2) are different.
8. The filter according to claim 1, characterized in that the first branch (Z1) and the second branch (Z2) have different lengths and widths.
9. The filter according to any of claims 1-8, characterized in that the two input ports (1) have the same port width and the same port length; the two output ports (2) have the same port width and the same port length.
10. A filter according to any of claims 1-8, characterized in that the input port (1) is an SMA connector and the output port (2) is an SMA connector.
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