CN111740188A - High Selectivity Balanced Bandpass Full Frequency Common Mode Rejection Intraband Common Mode Absorption Filter - Google Patents

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 Bandpass Full Frequency Common Mode Rejection Intraband Common Mode Absorption Filter

technical field

The invention relates to the field of electrical technology, in particular to a high-selectivity balanced band-pass full-frequency common-mode rejection common-mode absorption filter within a pass-band.

Background technique

With the development of communication technology, the fully balanced RF front-end in the communication system can better suppress common mode interference. Specifically, the balanced filter in the above-mentioned fully balanced radio frequency front end can suppress common mode noise and effectively suppress common mode interference, thereby improving the overall efficiency and anti-jamming capability of the communication system.

However, conventional balanced filters reflect common-mode noise while suppressing common-mode noise. Since the balanced filter is a part of the fully balanced RF front-end, the RF front-end will be full of common-mode noise, and the above-mentioned fully-balanced RF front-end contains many devices that are sensitive to common-mode noise, and the performance of the above-mentioned devices is easily affected by common-mode noise. The influence of noise, thereby affecting the communication performance of the fully balanced RF front-end and the communication performance of the communication system. Therefore, there is an urgent need for a filter that has good filtering characteristics and can reduce reflected common mode noise.

SUMMARY OF THE INVENTION

The purpose of the embodiments of the present invention is to provide a high-selectivity balanced band-pass full-frequency common-mode rejection in-band common-mode absorption filter, so as to have good filtering characteristics and reduce the reflection of common-mode noise. The specific technical solutions are as follows:

In a first aspect, embodiments of the present invention provide a high-selectivity balanced band-pass full-frequency common-mode rejection pass-band common-mode absorption filter, the filter includes: a dielectric substrate and 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, the branches are transmission lines with impedance, and the four branches include Two first branches Z1 and two second branches Z2, the four resistors include two first resistors R1 and two second resistors R2; wherein,

The input end of the first filter circuit structural unit 3 is connected to each input port 1 and one end of a second branch Z2, the other end of the second branch Z2 is connected to one end of a first resistor R1, and the one The other end of the first resistor R1 is grounded;

The output end of the first filter circuit structural unit 3 is connected to one end of each first branch Z1 and one end of a second resistor R2, and the other end of the one second resistor R2 is grounded;

The input end of the second filter circuit structural unit 4 is connected to the other end of each first branch Z1 and one end of the other second resistor R2, and the other end of the other 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, and the other end of the other second branch Z2 is connected to one end of another first resistor R1, The other end of the other first resistor R1 is grounded.

In an embodiment of the present invention, the first filter circuit structure unit 3 includes: two first filter circuit structure subunits 31 and a third branch Z3; wherein,

The first filter circuit structure subunit 31 includes: a first coupling line C1 including a line and a b line, a fourth branch Z4, a fifth branch Z5, and a sixth branch Z6; wherein:

One end of the b line in the first coupling line C1 is connected to one input port 1, and is connected to one end of the one fourth branch Z4, and the other end of the one fourth branch Z4 is connected to a third branch Z3. One end is connected; 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 the first branch Z1, and is connected with the One end of the a line in the first coupling line C1 is connected, the other end of the a line in the first coupling line C1 is connected with the one sixth branch Z6, and the other end of the one 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 the different first branch Z1.

In an embodiment of the present invention, the second filter circuit structure unit 4 includes: two second filter circuit structure subunits 41 and another third branch Z3; wherein,

The second filter circuit structure subunit 41 includes: a second coupling line C2 including a line and a b line, 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 is connected to one end of the other fourth branch Z4, and the other end of the other fourth branch Z4 is connected to another third branch One end of the node Z3 is connected; one end of the other fifth branch Z5 is connected with the other end of the other third branch Z3, and the other end of the other fifth branch Z5 is connected with the other end of the first branch Z1. The other end is connected to one end of the line a in the second coupling line C2, the other end of the line a in the second coupling line C2 is connected to one end of the other sixth branch Z6, the The other end of the other sixth branch Z6 is grounded;

One end of the other third branch Z3 is connected to one end of another second branch Z2, and the other end of the other third branch Z3 is connected to one end of another 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.

In an embodiment of the present invention, the first coupling line C1 and the second coupling line C2 have the same line width, the same slit width, and the same line length.

In an embodiment of the present invention, characteristic impedance values between 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 The lengths are not the same and the widths are not the same.

In an embodiment of the present invention, characteristic impedance values between the first branch Z1 and the second branch Z2 are different.

In an embodiment of the present invention, the length and width of the first branch Z1 and the second branch Z2 are different.

In an 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.

It can be seen from the above that because one end of the second branch Z2 in the filter provided by the embodiment of the present invention is connected to one end of the first resistor R1, the other end of the first resistor R1 is grounded, and the other end of the second branch Z2 passes through the circuit. The structural unit is connected to one end of the second resistor R2, 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 because in the balanced filter, when two resistors are grounded and the two grounding resistors are connected by branches, the balanced filter can suppress the common mode noise of the whole frequency band under the excitation of the common mode signal, and can also suppress all the noise. The reflected common-mode noise is converted into heat, effectively preventing common-mode noise from being reflected into the fully balanced RF front end. Therefore, the filter provided by the embodiment of the present invention reflects less common mode noise and can suppress the common mode noise in the whole frequency band. Therefore, the balanced filter provided by the embodiment of the present invention can reduce the reflection of common mode noise on the basis of having good filtering characteristics.

Of course, it is not necessary for any product or method of the present invention to achieve all of the advantages described above at the same time.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying 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. For those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative efforts.

1 is a schematic structural diagram of a first balanced filter provided by an embodiment of the present invention;

2 is a schematic structural diagram of a second type of balanced filter provided by an embodiment of the present invention;

3 is a schematic structural diagram of a third balanced filter provided by an embodiment of the present invention;

4 is a schematic structural diagram of a fourth balanced filter provided by an embodiment of the present invention;

FIG. 5 is a schematic diagram of dimensions of a dielectric substrate and a metal ground according to an embodiment of the present invention;

6a is a schematic diagram of a circuit structure of a balanced filter provided by an embodiment of the present invention;

6b is a partial schematic diagram of a corner of a coupling line in a balanced filter provided by an embodiment of the present invention;

6c is a partial schematic diagram of a connection between a resistor and a transmission line in a balanced filter provided by an embodiment of the present invention;

6d is a partial schematic diagram of the connection between a coupling line and a transmission line in a balanced filter provided by an embodiment of the present invention;

7 is a schematic diagram of an S-parameter simulation result of a balanced filter provided by an embodiment of the present invention under differential mode excitation;

FIG. 8 is a schematic diagram of an S-parameter simulation result of a balanced filter under common mode excitation provided by an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Referring to FIG. 1 , FIG. 1 is a schematic structural diagram of a first balanced filter provided by an embodiment of the present invention.

The balanced filter is used to receive the differential mode signal, and under the excitation of the differential mode signal, it exhibits band-pass filtering characteristics, and can suppress the common mode noise under the excitation of the common mode signal.

The above filter includes: a dielectric substrate and 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 resistance.

The above-mentioned branches are transmission lines with impedance. The above-mentioned four branches include two first branches Z1 and two second branches Z2. The above four resistors include two first resistors R1 and two second resistors R2.

In an embodiment of the present invention, the characteristic impedance values between 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 structural unit 3 and the second filter circuit structural unit 4 may be the same. Specifically, the connection relationship between the elements included in the first filter circuit structural unit 3 may be the same as the connection relationship between the elements included in the second filter circuit structural unit 4 .

In an embodiment of the present invention, the above-mentioned dielectric substrate may be TaconicCER-10, the dielectric constant of the dielectric substrate may be 10, the thickness may be 1.6 mm, and the dielectric loss may be 0.0035.

In an embodiment of the present invention, the port widths and port lengths of the two input ports 1 may be the same. The port widths and port lengths of the above two output ports 2 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 end of the first filter circuit structural unit 3 is connected to each input port 1 and one end of a second branch Z2, the other end of the second branch Z2 is connected to one end of a first resistor R1, the one The other end of the first resistor R1 is grounded.

The output end of the first filter circuit structural unit 3 is connected to 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 structure unit 4 is connected to the other end of each first branch Z1 and one end of another second resistor R2, and the other end of the other second resistor R2 is grounded.

The output end of the above-mentioned 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 other second branch Z2 is connected to one end of another first resistor R1, and the other end of the other second branch Z2 is connected. The other end of a first resistor R1 is grounded.

Because 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, and the other end of the second branch Z2 is connected to one end of the second resistor R2 through the circuit structure unit, 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. In addition, when two resistors are grounded in the balanced filter, and the two grounding resistors are connected by branches, under the excitation of the common mode signal, the above balanced filter can suppress the common mode noise in the whole frequency band, and can also reduce the balanced noise. The common-mode noise reflected by the filter is converted into heat, effectively preventing the common-mode noise from being reflected into the fully balanced RF front end. Therefore, the filter provided in this embodiment can suppress the common mode noise of the whole frequency band, and the reflected common mode noise is less.

Each of the above filter circuit structural units is a unit in the circuit structure of the filter, and after each of the above filter circuit structural units is connected in the above-mentioned circuit connection manner, a filter with better filtering characteristics can be obtained.

Since the above two input ports 1 are symmetrical and the two output ports 2 are symmetrical, the two input ports 1 may be called balanced input ports, and the two output ports 2 may be called balanced output ports.

In an embodiment of the present invention, due to the connection relationship between the first resistor R1, the second resistor R2, the first branch Z1, and the second branch Z2, the balanced filter can be excited by a common mode signal to the full frequency band. The common mode noise is suppressed, and the reflected common mode noise can also be converted into heat, thereby absorbing the common mode noise. Therefore, the parameter 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 balanced filter.

It can be seen from the above that because one end of the second branch Z2 in the filter provided in this embodiment is connected to one end of the first resistor R1, the other end of the first resistor R1 is grounded, and the other end of the second branch Z2 passes through the circuit structure. The unit is connected to one end of the second resistor R2, 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 because in the balanced filter, when two resistors are grounded and the two grounding resistors are connected by branches, the balanced filter can suppress the common mode noise of the whole frequency band under the excitation of the common mode signal, and can also suppress all the noise. The reflected common-mode noise is converted into heat, effectively preventing common-mode noise from being reflected into the fully balanced RF front end. Therefore, the common mode noise reflected by the filter provided in this embodiment is less, and the common mode noise of the whole frequency band can also be suppressed. Therefore, the balanced filter provided by the embodiment of the present invention can reduce the reflection of common mode noise on the basis of having good filtering characteristics.

Referring to FIG. 2, FIG. 2 is a schematic structural diagram of a second balanced filter provided by an embodiment of the present invention. On the basis of the foregoing embodiment, the foregoing first filter circuit structure unit 3 may include: two first filter circuit structure subunits 31 and one third branch Z3.

The first filter circuit structure subunit 31 includes: a first coupling line C1 including a line and a b line, a fourth branch Z4, a fifth branch Z5, and a sixth branch Z6.

Since the above-mentioned first coupling line C1 includes two transmission lines with a short distance, in order to distinguish the two lines in the above-mentioned first coupling line C1 with a short distance, one of the lines can be used as line a, and the other line can be used as line b .

In an embodiment of the present invention, the electrical length of the first coupling line C1 may be 90°.

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 may be different.

In an embodiment of the present invention, the length and width of the fourth branch Z4 and the fifth branch Z5 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 line b in the first coupling line C1 is connected to one input port 1 and is connected to one end of one fourth branch Z4.

The other end of the above-mentioned one fourth branch Z4 is connected to one end of a third branch Z3.

One end of the above-mentioned one fifth branch Z5 is connected with the other end of the above-mentioned one third branch Z3, and the other end of the above-mentioned one fifth branch Z5 is connected with one end of a first branch Z1, and is connected with the first coupling line C1. Connect one end of the a wire.

The other end of the line a in the first coupling line C1 is connected to the one sixth branch Z6, and the other end of the one sixth branch Z6 is grounded.

One end of the above-mentioned one third branch Z3 is connected to one end of the above-mentioned one second branch Z2, and the other end of the above-mentioned one third branch Z3 is connected to one end of the above-mentioned one second resistor R2.

Wherein, 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.

Because the first filter circuit structural unit 3 includes the first coupling line C1, the other end of the line a in the first coupling line C1 is connected to the one sixth branch Z6, and the other end of the one sixth branch Z6 is grounded . In addition, when the input port in the filter is connected to the coupling line, and one line in the coupling line is connected to a ground branch, the filtering bandwidth can be widened and the transmission pole can be increased, so that the filtering bandwidth of the filter is wider and has high selectivity. Therefore, the filter provided in this embodiment has a wide filtering bandwidth and high selectivity.

In an embodiment of the present invention, due to the connection relationship between the first coupling line C1 and the sixth branch Z6, the filter has a wide filtering bandwidth and high selectivity. Therefore, the parameter values of the above-mentioned first coupling line C1 and the sixth branch Z6 may be related to the performance constraint value of the above-mentioned filter.

Referring to FIG. 3 , FIG. 3 is a schematic structural diagram of a third balanced filter provided by an embodiment of the present invention. On the basis of the above-mentioned embodiment, the above-mentioned second filter circuit structure unit 4 includes: two second filter circuit structure subunits 41 and another third branch Z3;

The above-mentioned second filter circuit structure subunit 41 includes: a second coupling line C2 including a line and a b line, another fourth branch Z4, another fifth branch Z5, and another sixth branch Z6.

Since the above-mentioned second coupling line C2 includes two transmission lines with a short distance, in order to distinguish the two lines in the above-mentioned second coupling line C2 with a short distance, one of the lines can be used as line a, and the other line can be used as line b .

In an embodiment of the present invention, the electrical length of the second coupling line C2 may be 90°.

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 may be different.

In an embodiment of the present invention, the length and width of the fourth branch Z4 and the fifth branch Z5 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 line b in the second coupling line C2 is connected to one output port 2 and is connected to one end of another fourth branch Z4.

The other end of the above-mentioned 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, and the other end of the other fifth branch Z5 is connected to the other end of the first branch Z1, and is connected to the second coupling line One end of the a wire in C2 is connected.

The other end of the line a in the second coupling line C2 is connected to one end of the other sixth branch Z6.

The other end of the above-mentioned other sixth branch Z6 is grounded.

One end of the other third branch Z3 is connected to one end of the other second branch Z2, and the other end of the other third branch Z3 is connected to one end of the other second resistor R2.

Wherein, 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.

Because the second filter circuit structural unit 4 includes the second coupling line C2, the other end of the line a in the second coupling line C2 is connected to the sixth branch Z6, and the other end of the sixth branch Z6 is grounded. In addition, when the output port in the filter is connected to the coupling line, and one line in the coupling line is connected to a ground branch, the filtering bandwidth can be widened and the transmission pole can be increased, so that the filtering bandwidth of the filter is wider and has high selectivity. Therefore, the filter provided in this embodiment has a wide filtering bandwidth and high selectivity.

In an embodiment of the present invention, due to the connection relationship between the second coupling line C2 and the sixth branch Z6, the filter has a wide 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 constraints of the filter.

In an embodiment of the present invention, the above-mentioned filter can be constructed on a single-layer printed circuit board. Specifically, the filter can be constructed by using a design method of a single-layer printed circuit board. The top layer of the circuit board is the filter circuit structure, and the bottom layer is the metal ground plane.

In this way, the constructed filter has a simple overall 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 provided by an embodiment of the present invention. FIG. 4 includes: 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.

The above-mentioned four branches include two first branches Z1 and two second branches Z2.

The above four resistors include two first resistors R1 and two second resistors R2.

Specifically, the input end of the first filter circuit structural unit 3 is connected to each input port 1 and one end of a second branch Z2, the other end of the second branch Z2 is connected to one end of a first resistor R1, the one The other end of the first resistor R1 is grounded.

The output end of the first filter circuit structural unit 3 is connected to 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 structure unit 4 is connected to the other end of each first branch Z1 and one end of another second resistor R2, and the other end of the other second resistor R2 is grounded.

The output end of the above-mentioned 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 other second branch Z2 is connected to one end of another first resistor R1, and the other end of the other second branch Z2 is connected. The other end of a first resistor R1 is grounded.

Specifically, the above-mentioned first filter circuit structural unit 3 includes: two first filter circuit structural subunits 31 and one third branch Z3.

The first filter circuit structure subunit 31 includes: a first coupling line C1 including a line and a b line, a fourth branch Z4, a fifth branch Z5, and a sixth branch Z6.

One end of line b in the first coupling line C1 is connected to one input port 1 and one end of one fourth branch Z4.

The other end of the above-mentioned one fourth branch Z4 is connected to one end of a third branch Z3.

One end of the above-mentioned one fifth branch Z5 is connected with the other end of the above-mentioned one third branch Z3, and the other end of the above-mentioned one fifth branch Z5 is connected with one end of a first branch Z1, and is connected with the first coupling line C1. Connect one end of the a wire.

The other end of the line a in the first coupling line C1 is connected to the one sixth branch Z6, and the other end of the one sixth branch Z6 is grounded.

One end of the above-mentioned one third branch Z3 is connected to one end of the above-mentioned one second branch Z2, and the other end of the above-mentioned one third branch Z3 is connected to one end of the above-mentioned one second resistor R2.

Wherein, 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 above-mentioned second filter circuit structure unit 4 includes: two second filter circuit structure subunits 41 and another third branch Z3;

The above-mentioned second filter circuit structure subunit 41 includes: a second coupling line C2 including a line and a b line, another fourth branch Z4, another fifth branch Z5, and another sixth branch Z6.

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 other fourth branch Z4.

The other end of the above-mentioned 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, and the other end of the other fifth branch Z5 is connected to the other end of the first branch Z1, and is connected to the second coupling line One end of the a wire in C2 is connected.

The other end of the 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 to one end of the other second branch Z2, and the other end of the other third branch Z3 is connected to one end of the other second resistor R2.

Wherein, 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, since each element and connection relationship in the above-mentioned balanced filter are symmetrical up, down, left and right, the balanced filter provided in this embodiment is a filter with a symmetrical structure up and down.

Referring to FIG. 5 , FIG. 5 is a schematic diagram of dimensions of a dielectric substrate and a metal ground according to an embodiment of the present invention. It can be seen from Figure 5 that the size of the metal ground and the dielectric substrate are the same.

Specifically, in FIG. 5 , _La represents the lateral width of the metal ground and the dielectric substrate, and Wa represents the vertical width of the metal ground and the dielectric substrate. W _b is the horizontal excavation depth of the upper left, lower left, upper right and lower right corners of the metal ground and the dielectric substrate, and L _b is the longitudinal excavation depth of the four upper left, lower left, upper right and lower right corners of the metal ground and the dielectric substrate.

In the figure, the above-mentioned La may be 55.8 mm, W _a may be _{29 mm, L b may be 7.75 mm, and W b may be} 6.5 mm.

Since the size of the above-mentioned dielectric substrate is small, and the circuit structure on the dielectric substrate is simple, it is easy to process and integrate, and the circuit structure is planar, and can be widely used in fully balanced radio frequency front-ends.

Referring to FIG. 6a, FIG. 6a is a schematic diagram of a circuit structure of a balanced filter provided by an embodiment of the present invention.

The trapezoidal boxes at the upper left corner and the lower left corner of FIG. 6a are input ports respectively, and the trapezoidal boxes at the upper right corner and the lower right corner are respectively output ports. Among them, 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, the aforementioned Wp may be 1.5 mm, and the aforementioned Lp may be 8.2 mm.

In the upper left corner and the lower left corner of the trapezoidal frame in FIG. 6a, there are two transmission lines with similar distances adjacent to the right side, and the above two transmission lines with similar distances are coupling lines. There are two transmission lines with similar distances adjacent to the left side of the trapezoidal frame at the upper right corner and the lower right corner, and the above two transmission lines with similar distances are coupling lines. Among them, We is the line width of the coupling line, _Se is the _slit width of the coupling line, and Le is the thread of the coupling line. The line width, slot width and line length of the four coupling lines are equal. Specifically, the We may be 0.1 mm, the _Se may be 0.15 mm, and the _Le may be 9 mm.

Among the above coupling lines, the transmission line connected to the input port or the output port is the b line, and the transmission line not connected to the input port or the output port in the above coupling line is the a line. Therefore, in the upper half of Fig. 6a, the upper transmission line in the coupled line is line a, the lower transmission line in the coupled line is line b; the lower transmission line in the coupled line is line b. In the lower half of Fig. 6a, the lower transmission line in the coupled lines is line a, and the upper transmission line in the coupled line is line b. In FIG. 6a, the circular frame close to the line a is a grounding hole. Specifically, the line a is grounded through a short-circuit line, (L _s1 +L _s2 ) is the length of the short-circuit line, and Ws is the width of the short-circuit line. Specifically, the above (L _s1 +L _s2 ) may be 8.6 mm, and the above Ws may be 0.1 mm.

In the upper half of Fig. 6a, the right end of the line a in the left coupling line and the left end of the line a in the right coupling line are connected by a horizontal transmission line. In the lower half of Fig. 6a, the right end of line a in the left coupling line and the left end of line a in the right coupling line are connected by a horizontal transmission line. Wherein, L ₃ is the length of the transmission line, and W ₃ is the width of the transmission line. The above two transmission lines have the same length and width. Specifically, L ₃ may be 8 mm, and the above W ₃ may be 0.1 mm.

In the left half of Fig. 6a, the line a in the upper coupling line and the line a in the lower coupling line are connected by two vertical transmission lines. In the right half of Fig. 6a, the line a in the upper coupling line and the line a in the lower coupling line are connected by two vertical transmission lines. Wherein, L ₂ is the length of each of the above-mentioned two transmission lines, and W ₂ is the width of each of the above-mentioned two transmission lines. Specifically, L ₂ may be 9.5mm, and W ₂ may be 0.4mm.

In the left half of Fig. 6a, the two trapezoidal boxes are connected by two transmission lines, and in the right half of Fig. 6b, the two trapezoidal boxes are connected by two transmission lines. Wherein, L ₁ is the length of each of the above-mentioned two transmission lines, and W ₁ is the width of each of the above-mentioned two transmission lines. Specifically, L ₁ may be 9.5 mm, and W ₁ may be 0.4 mm.

In Fig. 6a, there are four rectangular frames, and each rectangular frame has three circles, and the circles in each rectangular frame are grounding holes. The resistor R ₁ is connected to the rectangular frame in the middle vertical direction in FIG. 6 a , and the resistor R ₂ is connected to the rectangular frame in the horizontal direction on both sides of FIG. 6 a . The lengths of the resistor R ₁ and the resistor R ₂ are the same, wherein _S1 is the length of the resistor R ₁ and the resistor R ₂ .

In FIG. 6a, the resistor R ₁ and the resistor R ₂ are connected by two transmission lines, wherein L ₄ is the length of the transmission line, and W ₄ is the width of the above-mentioned transmission line. L _t is the length of another transmission line, and Wt is the width of the other transmission line. Specifically, the above-mentioned L ₄ may be 7 mm, W ₄ may be 0.1 mm, W ₄ may be 7.4 mm, and L _t may be 0.4 mm.

The dashed box on the upper side in Fig. 6a corresponds to Fig. 6b, the dashed box on the middle side in Fig. 6b corresponds to Fig. 6c, and the dashed box on the lower side in Fig. 6a corresponds to Fig. 6d.

Referring to FIG. 6b, FIG. 6b is a partial schematic diagram of a corner of a coupling line in a balanced filter provided by an embodiment of the present invention.

In Fig. 6b, the rectangular box on the left is the input port, and the two adjacent transmission lines on the right side of the rectangular box with a small distance are the coupling lines. Wherein, the transmission line connected to the rectangular frame in the above coupling lines is the b line, and the transmission line not connected to the rectangular frame in the above coupling lines is the a line. There is a square frame above the A line, and there is a circle in the square frame, and the above-mentioned circle is a grounding hole. The a-line is grounded through the short-circuit line, (L _s1 +L _s2 ) is the length of the short-circuit line, and Ws is the width of the short-circuit line. Specifically, the above (L _s1 +L _s2 ) may be 8.6 mm, and the above Ws may be 0.1 mm. Wp is the width of the input port, and the above Wp may be 1.5mm.

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 provided by an embodiment of the present invention.

The circles in the left and right rectangular frames in Figure 6c are grounding holes, the resistor R1 is connected to the left rectangular frame, the resistor R2 is connected to the right rectangular frame, and the resistor _R1 and the resistor R2 are connected by _two transmission lines, L _t is the length of the left transmission line and _W4 is the width of the right transmission line. S ₁ is the length of the resistor R ₁ and the resistor R ₂ . Specifically, the aforementioned W ₄ may be 0.1 mm, and the aforementioned L _t may be 0.4 mm.

Referring to FIG. 6d, FIG. 6d is a partial schematic diagram of a connection between a coupling line and a transmission line in a balanced filter provided by an embodiment of the present invention.

In Figure 6d, the two lines that are closer to the left are the coupling lines, the rectangular frame is the grounding hole, the line connected to the grounding hole in the coupling line is line a, and the line that is not connected to the grounding hole in the coupling line is line b. Wherein, We is the line width of the coupling line, _Se is the slot _width of the coupling line, and L ₃ is the length of the transmission line connected to the a line. Specifically, We may be 0.1 mm, the above _Se may be 0.15 mm, and L ₃ may be 8 mm.

Referring to FIG. 7 , FIG. 7 is a schematic diagram of an S-parameter simulation result of a balanced filter under differential mode excitation provided by an embodiment of the present invention. In Figure 7, the abscissa is the frequency, and the unit is GHz, and the ordinate is the S parameter value, and the unit is: dB.

It can be obtained from Figure 7 that when the frequency is 3.5GHz, the insertion loss Sdd21 is -0.4dB, the range of the insertion loss Sdd21 greater than -3dB is 2.11GHz to 4.80GHz, the 3dB bandwidth is 2.69GHz, and the 3dB relative bandwidth is 76.86%. Therefore, the filter can achieve broadband filtering performance and achieve small insertion loss.

At the frequency of 3.5GHz, the return loss Sdd11 is -16.18dB, the return loss Sdd11 is less than -15dB, the range is 2.58GHz to 4.72GHz, the bandwidth is 2.14GHz, the relative bandwidth is 61.15%, the return loss Sdd11 is less than -10dB The range is 2.47GHz to 4.75GHz, the bandwidth is 2.28GHz, and the relative bandwidth is 65.15%.

The four reflection zeros are located at 2.76GHz, 3.96GHz, 4.38GHz and 4.64GHz respectively, and the return loss Sdd11 at the reflection zeros is -37.58dB, -39.02dB, -41.12dB and -36.20dB respectively. High selectivity of the filtering performance of the balanced bandpass filter under differential mode excitation. At the same time, the relative bandwidth of the filter is relatively wide, and a better wide-band differential mode response can be achieved.

Referring to FIG. 8 , FIG. 8 is a schematic diagram of an S-parameter simulation result of a balanced filter under common mode excitation provided by an embodiment of the present invention. In Figure 8, the abscissa is the frequency, and the unit is GHz, and the ordinate is the S parameter value, and the unit is: dB.

It can be concluded from Figure 8 that when the frequency is 3.5GHz, the insertion loss Scc21 is -27.89dB, and at 3.7GHz, the insertion loss Scc21 is -54.22dB, which can achieve deep suppression of common mode noise.

In the frequency range of 0-8GHz, the insertion loss Scc21 is less than -14.58dB, which can achieve the suppression effect of common mode noise in the whole frequency range, and effectively suppress the transmission of common mode noise in the whole frequency range.

When the frequency is 3.5GHz, the return loss Scc11 is -45dB, the return loss Scc11 is less than -10dB in the range of 2.32GHz to 4.43GHz, the bandwidth is 2.11GHz, the relative bandwidth is 60.3%, the return loss Scc11 is less than -15dB The range is 3.08GHz to 4.16GHz with a relative bandwidth of 30.86%. At 3.72GHz, the return loss Scc11 is -54.67dB, which can effectively absorb common mode noise. By introducing a grounding resistance to convert the reflected common-mode noise into heat, it can effectively prevent the common-mode noise from being reflected into the balanced system and affect the performance of other microwave devices. The 10dB absorption bandwidth of common mode noise here is 60.3%, indicating that the filter can achieve broadband common mode noise absorption. At 3.72GHz, the return loss Scc11 is -54.67dB, indicating that the filter can effectively absorb common mode noise. , the absorption effect is better.

It should be noted that, in this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any relationship between these entities or operations. any such actual relationship or sequence exists. Moreover, the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that a process, method, article or device that includes a list of elements includes not only those elements, but also includes not explicitly listed or other elements inherent to such a process, method, article or apparatus. Without further limitation, an element qualified by the phrase "comprising a..." does not preclude the presence of additional identical elements in a process, method, article or apparatus that includes the element.

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 principle of the present invention are included in the protection scope of the present invention.

Claims (10)

1. A high-selectivity balanced band-pass full-frequency common-mode rejection pass-band common-mode absorption filter, wherein the filter comprises: a dielectric substrate and 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, the branches are transmission lines with impedance, and the The four branches include two first branches (Z1) and two second branches (Z2), and the four resistors include two first resistors (R1) and two second resistors (R2); wherein, The input end of the first filter circuit structural unit (3) is connected to each input port (1) and one end of a second branch (Z2), and the other end of the second branch (Z2) is connected to a first resistor One end of (R1) is connected, and the other end of the one first resistor (R1) is grounded; The output end of the first filter circuit structural unit (3) is connected to one end of each first branch (Z1) and one end of a second resistor (R2), and the other end of the one second resistor (R2) is grounded ; The input end of the second filter circuit structural unit (4) is connected to the other end of each first branch (Z1) and one end of another second resistor (R2), and the other end of the other second resistor (R2) The other end 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), and the other end of the other second branch (Z2) is connected to another One end of the first resistor (R1) is connected, and the other end of the other first resistor (R1) is grounded. 2. The filter according to claim 1, wherein the first filter circuit structural unit (3) comprises: two first filter circuit structural subunits (31) and a third branch (Z3) ;in, The first filter circuit structure subunit (31) includes: a first coupling line (C1) including a line and a b line, a fourth branch (Z4), a fifth branch (Z5), and a sixth branch ( Z6); where: One end of the b line in the first coupling line (C1) is connected to one input port (1), and is connected to one end of the one fourth branch (Z4), and the other end of the one fourth branch (Z4) connected with one end of the one third branch (Z3); one end of the one fifth branch (Z5) is connected with the other end of the one third branch (Z3), the one fifth branch (Z5) The other end of (Z5) is connected to one end of a first branch (Z1), and is connected to one end of the a line in the first coupling line (C1), and the a in the first coupling line (C1) The other end of the wire is connected to the one sixth branch (Z6), and the other end of the one 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 the one end of the one second resistor (R2). one end connection; 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 the different first branch (Z1) connect. 3. The filter according to claim 2, wherein the second filter circuit structure unit (4) comprises: two second filter circuit structure subunits (41) and another third branch (Z3) );in, The second filter circuit structure subunit (41) includes: a second coupling line (C2) including a line and a b line, another fourth branch (Z4), another fifth branch (Z5), another first branch Six branches (Z6); of which: 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 other fourth branch (Z4), and the other fourth branch (Z4) The other end is connected with one end of another third branch (Z3); one end of the other fifth branch (Z5) is connected with the other end of the other third branch (Z3), and the other The other end of the five branches (Z5) is connected to the other end of a first branch (Z1), and is connected to one end of the line a in the second coupling line (C2), and the second coupling line (C2) The other end of the a-line 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 to one end of the other second branch (Z2), and the other end of the other third branch (Z3) is connected to the other end of the second resistor (R2). one end connection; The second coupling lines (C2) in the two second filter circuit structure sub-units (41) are connected to different output ports (2), and the fifth branch (Z5) is connected to the other of the different first branch (Z1). connected at one end. 4. The filter according to claim 3, characterized in that the first coupling line (C1) and the second coupling line (C2) have the same line width, the same slit width, and the same line length. 5. The filter according to claim 3, characterized in that, the third branch (Z3), the fourth branch (Z4), the fifth branch (Z5) and the sixth branch ( The characteristic impedance values between Z6) are different. 6. The filter according to claim 3, wherein the fourth branch (Z4) and the fifth branch (Z5) have the same length and the same width, and the third branch (Z3), The length and width of the fourth branch (Z4) and the sixth branch (Z6) are different. 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 length and width of the first branch (Z1) and the second branch (Z2) are different. 9. The filter according to any one of claims 1-8, wherein 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; The port width is the same and the port length is the same. 10. The filter according to any one of claims 1-8, wherein the input port (1) is an SMA connector, and the output port (2) is an SMA connector.

Images