A broadband balanced notch filter with differential mode non-reflection characteristics

Abstract

The invention discloses a broadband balanced notch filter with differential mode non-reflection characteristics, comprising: a balanced differential input port A, a balanced differential output port B, four groups of non-reflection absorption branches, four sections of quarter-wavelength signal transmission lines, four sections of quarter-wavelength anti-connected wiring, four sections of quarter-wavelength filter coupling lines, two sections of quarter-wavelength zero point short-circuit lines, two common-mode absorption resistors, two sections of quarter-wavelength notch coupling lines and four notch absorption resistors. In addition to being able to effectively suppress common-mode noise, the balanced filter introduces a first-order deep notch at the center frequency of the filter, achieving the suppression effect of interference signals within the filter band, and introduces two transmission zeros in the stop band of the filter, thereby enhancing the steepness and filtering selectivity of the transition band of the differential balanced filter, and at the same time achieving the non-reflection characteristics of out-of-band signals under differential mode signal excitation, thereby improving the overall performance of the balanced filter.

Description

Technical Field

[0001] The invention relates to a balanced filter, in particular to a broadband balanced notch filter with differential mode non-reflection characteristics. Background Art

[0002] Balanced circuits play an important role in modern wireless communication systems. Compared with unbalanced single-port input and output circuits, balanced circuits can effectively suppress environmental noise and noise generated by internal active devices, and thus have superior electromagnetic compatibility characteristics. Various RF microwave devices, such as filters, mixers, and power amplifiers, are widely designed as balanced topologies. With the rapid development of integrated circuits, the demand for balanced devices will become more urgent. Balanced filters have filtering characteristics when differential mode signals are input, and can effectively suppress common mode noise. Balanced filters can be easily constructed with a single-port filter and two baluns, but their area is huge. Therefore, it is very important to design balanced filters as a single device without adding additional baluns, which has broad application prospects.

[0003] Conventional filters are reflective filters, which achieve the purpose of filtering by reflecting the energy of unnecessary frequency components back to the signal source, thus realizing frequency selection. In nonlinear systems, the mixing of reflected echo signals with existing signals will generate many interference signals, which will have a huge impact on the performance of the system. In order to solve the negative impact of conventional filters, attenuators are generally cascaded in front of conventional filters, and amplifiers are cascaded after them, so as to minimize the impact of reflected wave signals from conventional filters. Reflectionless filters can solve the problems of conventional filters. They can effectively absorb out-of-band signals through resistors and then dissipate them in the form of heat, reducing the reflected wave energy of out-of-band signals, thereby improving the overall performance of the system.

[0004] A notch filter is a filter that can quickly attenuate the input signal in a narrow frequency band to prevent the signal in this frequency band from passing through. It is usually used in the design of ultra-wideband filters to filter out interference frequency band signals in the passband. However, most of the existing notch filter research is based on the premise of ultra-wideband technology application, and then introduces band-stop branches on the basis of the ultra-wideband filter structure to achieve the notch effect. There are few studies that design notch filters as an independent passive device. Therefore, the existing notch filters have more or less many problems such as large filter structure size, poor selectivity, insufficient steepness of the transition band near the notch frequency band in the passband, and poor out-of-band suppression of the overall filter. In addition, it is impossible to eliminate the impact of the energy reflected back to the input end of the out-of-band signal on the performance of the front-end system. Therefore, it is of great significance to study the performance expansion of a balanced notch filter that has high performance in differential mode and can achieve common mode suppression and realize the reflection-free characteristics. In view of this, it is necessary to propose a broadband balanced notch filter with differential mode reflection-free characteristics. Summary of the invention

[0005] Based on this, in order to solve the shortcomings of the existing technology, a broadband balanced notch filter with differential mode non-reflection characteristics is proposed. It includes: a balanced differential input port A, a balanced differential output port B, four groups of non-reflection absorption branches, four quarter-wavelength signal transmission lines, four quarter-wavelength anti-connected wirings, four quarter-wavelength filter coupling lines, two quarter-wavelength zero short-point lines, two common-mode absorption resistors, two quarter-wavelength notch coupling lines and four notch absorption resistors;

[0006] The balanced differential input port A includes an input port A+ and an input port A-;

[0007] The balanced differential output port B includes an output port B+ and an output port B-;

[0008] The four groups of non-reflection absorbing branches include a first non-reflection absorbing branch, a second non-reflection absorbing branch, a third non-reflection absorbing branch and a fourth non-reflection absorbing branch;

[0009] The four quarter-wavelength signal transmission lines include a first signal transmission line, a second signal transmission line, a third signal transmission line and a fourth signal transmission line; wherein one end of the first signal transmission line is connected to the input port A+, and the other end is connected to the connection between the first anti-connecting wiring and the first filter coupling line; one end of the second signal transmission line is connected to the input port A-, and the other end is connected to the connection between the second anti-connecting wiring and the second filter coupling line; one end of the third signal transmission line is connected to the output port B+, and the other end is connected to the connection between the third anti-connecting wiring and the third filter coupling line; one end of the fourth signal transmission line is connected to the output port B-, and the other end is connected to the connection between the fourth anti-connecting wiring and the fourth filter coupling line;

[0010] The four quarter-wavelength anti-connected wirings include a first anti-connected wiring, a second anti-connected wiring, a third anti-connected wiring and a fourth anti-connected wiring; wherein one end of the first anti-connected wiring is connected to the connection between the first signal transmission line and the first filter coupling line, and the other end is connected to the second anti-connected wiring; one end of the second anti-connected wiring is connected to the connection between the second signal transmission line and the second filter coupling line, and the other end is connected to the first anti-connected wiring; one end of the third anti-connected wiring is connected to the connection between the third signal transmission line and the third filter coupling line, and the other end is connected to the fourth anti-connected wiring; one end of the fourth anti-connected wiring is connected to the connection between the fourth signal transmission line and the fourth filter coupling line, and the other end is connected to the third anti-connected wiring;

[0011] The four-section quarter-wavelength filter coupling lines include a first filter coupling line, a second filter coupling line, a third filter coupling line and a fourth filter coupling line; the A port of the first filter coupling line is connected to the connection between the first signal transmission line and the first anti-connection wiring; the A port of the second filter coupling line is connected to the connection between the second signal transmission line and the second anti-connection wiring; the A port of the third filter coupling line is connected to the connection between the third signal transmission line and the third anti-connection wiring; the A port of the fourth filter coupling line is connected to the connection between the fourth signal transmission line and the fourth anti-connection wiring; the D port of the first filter coupling line is connected to the D port of the third filter coupling line; the D port of the second filter coupling line is connected to the D port of the fourth filter coupling line;

[0012] The two quarter-wavelength zero-point short-circuit lines include a first zero-point short-circuit line and a second zero-point short-circuit line; wherein one end of the first zero-point short-circuit line is connected to the connection between the first filter coupling line and the third filter coupling line, and the other end is grounded; one end of the second zero-point short-circuit line is connected to the connection between the second filter coupling line and the fourth filter coupling line, and the other end is grounded;

[0013] The two common-mode absorption resistors include a first common-mode absorption resistor and a second common-mode absorption resistor; wherein one end of the first common-mode absorption resistor is connected to the connection point between the first anti-connected wiring and the second anti-connected wiring, and the other end is grounded; one end of the second common-mode absorption resistor is connected to the connection point between the third anti-connected wiring and the fourth anti-connected wiring, and the other end is grounded;

[0014] The two quarter-wavelength notch coupling lines include a first notch coupling line and a second notch coupling line; the A port of the first notch coupling line is connected to the first notch absorption resistor; the B port of the first notch coupling line is connected to the third notch absorption resistor; the C port and the D port of the first notch coupling line are both grounded; the A port of the second notch coupling line is connected to the second notch absorption resistor; the B port of the second notch coupling line is connected to the fourth notch absorption resistor; the C port and the D port of the second notch coupling line are both grounded;

[0015] The four trap absorption resistors include a first trap absorption resistor, a second trap absorption resistor, a third trap absorption resistor and a fourth trap absorption resistor; one end of the first trap absorption resistor is connected to the C port of the first filter coupling line, and the other end is connected to the A port of the first trap coupling line; one end of the second trap absorption resistor is connected to the C port of the second filter coupling line, and the other end is connected to the A port of the second trap coupling line; one end of the third trap absorption resistor is connected to the C port of the third filter coupling line, and the other end is connected to the B port of the first trap coupling line; one end of the fourth trap absorption resistor is connected to the C port of the fourth filter coupling line, and the other end is connected to the B port of the second trap coupling line;

[0016] The first reflectionless absorption branch, the second reflectionless absorption branch, the third reflectionless absorption branch and the fourth reflectionless absorption branch have the same structure; the first reflectionless absorption branch includes a reflectionless absorption transmission line, a reflectionless absorption terminal open line and a reflectionless absorption resistor; one end of the reflectionless absorption transmission line is connected to the connection between the input port A+ and the first signal transmission line, and the other end is connected to the B port of the first filter coupling line; one end of the reflectionless absorption terminal open line is connected to the connection between the reflectionless absorption transmission line and the first filter coupling line, and the other end is open; one end of the reflectionless absorption resistor is connected to the connection between the reflectionless absorption transmission line and the first filter coupling line, and the other end is short-circuited.

[0017] The reflection-free characteristic of the out-of-band differential mode signal is adjusted by adjusting the first reflection-free absorption branch, the second reflection-free absorption branch, the third reflection-free absorption branch and the fourth reflection-free absorption branch.

[0018] The filtering characteristics of the differential mode signal are adjusted by adjusting the first filtering coupling line, the second filtering coupling line, the third filtering coupling line and the fourth filtering coupling line.

[0019] The out-of-band transmission zero point of the differential mode signal is adjusted by adjusting the first zero point short-circuit line and the second zero point short-circuit line.

[0020] The in-band suppression characteristics of the common-mode signal are adjusted by adjusting the first common-mode absorption resistor and the second common-mode absorption resistor.

[0021] The notch characteristic of the differential mode signal at the center frequency is adjusted by adjusting the first notch absorption resistor, the second notch absorption resistor, the third notch absorption resistor and the fourth notch absorption resistor.

[0022] In order to design a balanced filter as a single device, and to improve the differential mode filtering performance of the balanced notch filter and realize the non-reflection characteristic under the excitation of the differential mode signal, the present invention provides a broadband balanced notch filter with differential mode non-reflection characteristics. In addition to being able to effectively suppress common mode noise, the balanced filter introduces a first-order deep notch at the center frequency of the filter, thereby achieving the suppression effect of the interference signal within the filter band, and introduces two transmission zeros in the stop band of the filter, thereby enhancing the steepness and filtering selectivity of the transition band of the differential balanced filter, and at the same time realizing the non-reflection characteristic of the out-of-band signal under the excitation of the differential mode signal, thereby improving the overall performance of the balanced filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a structural schematic diagram of a broadband balanced notch filter with differential mode non-reflection characteristics of the present invention;

[0025] Figure 2 It is a mixed S parameter amplitude curve diagram of a broadband balanced notch filter with differential mode non-reflection characteristics under differential mode signal excitation of the present invention;

[0026] Figure 3 The invention discloses a mixed S parameter amplitude curve diagram of a broadband balanced notch filter with differential mode non-reflection characteristics under common mode signal excitation. DETAILED DESCRIPTION

[0027] In order to make the technical solutions and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention:

[0028] The invention discloses a broadband balanced notch filter with differential mode non-reflection characteristics, comprising: a balanced differential input port A, a balanced differential output port B, four groups of non-reflection absorption branches, four sections of quarter-wavelength signal transmission lines, four sections of quarter-wavelength anti-connected wiring lines, four sections of quarter-wavelength filter coupling lines, two sections of quarter-wavelength zero-point short-circuit lines, two common-mode absorption resistors, two sections of quarter-wavelength notch coupling lines and four notch absorption resistors;

[0029] The balanced differential input port A includes an input port A+1 and an input port A-2;

[0030] The balanced differential output port B includes an output port B+3 and an output port B-4;

[0031] The four groups of non-reflection absorbing branches include a first non-reflection absorbing branch 5, a second non-reflection absorbing branch 6, a third non-reflection absorbing branch 7 and a fourth non-reflection absorbing branch 8;

[0032] The four quarter-wavelength signal transmission lines include a first signal transmission line 9, a second signal transmission line 10, a third signal transmission line 11 and a fourth signal transmission line 12; wherein one end of the first signal transmission line 9 is connected to the input port A+1, and the other end is connected to the connection between the first anti-connection wiring 13 and the first filter coupling line 17; one end of the second signal transmission line 10 is connected to the input port A-2, and the other end is connected to the connection between the second anti-connection wiring 14 and the second filter coupling line 18; one end of the third signal transmission line 11 is connected to the output port B+3, and the other end is connected to the connection between the third anti-connection wiring 15 and the third filter coupling line 19; one end of the fourth signal transmission line 12 is connected to the output port B-4, and the other end is connected to the connection between the fourth anti-connection wiring 16 and the fourth filter coupling line 20;

[0033] The four quarter-wavelength anti-connected wirings include a first anti-connected wiring 13, a second anti-connected wiring 14, a third anti-connected wiring 15 and a fourth anti-connected wiring 16; wherein one end of the first anti-connected wiring 13 is connected to the connection between the first signal transmission line 9 and the first filter coupling line 17, and the other end is connected to the second anti-connected wiring 14; one end of the second anti-connected wiring 14 is connected to the connection between the second signal transmission line 10 and the second filter coupling line 18, and the other end is connected to the first anti-connected wiring 13; one end of the third anti-connected wiring 15 is connected to the connection between the third signal transmission line 11 and the third filter coupling line 19, and the other end is connected to the fourth anti-connected wiring 16; one end of the fourth anti-connected wiring 16 is connected to the connection between the fourth signal transmission line 12 and the fourth filter coupling line 20, and the other end is connected to the third anti-connected wiring 15;

[0034] The four quarter-wavelength filter coupling lines include a first filter coupling line 17, a second filter coupling line 18, a third filter coupling line 19 and a fourth filter coupling line 20; the A port 1a of the first filter coupling line 17 is connected to the connection between the first signal transmission line 9 and the first anti-connection connection line 13; the A port 2a of the second filter coupling line 18 is connected to the connection between the second signal transmission line 10 and the second anti-connection connection line 14; the A port 3a of the third filter coupling line 19 is connected to the connection between the third signal transmission line 11 and the third anti-connection connection line 15; the A port 4a of the fourth filter coupling line 20 is connected to the connection between the fourth signal transmission line 12 and the fourth anti-connection connection line 16; the D port 1d of the first filter coupling line 17 is connected to the D port 3d of the third filter coupling line 19; the D port 2d of the second filter coupling line 18 is connected to the D port 4d of the fourth filter coupling line 20;

[0035] The two quarter-wavelength zero-point short-circuit lines include a first zero-point short-circuit line 21 and a second zero-point short-circuit line 22; wherein one end of the first zero-point short-circuit line 21 is connected to the connection between the first filter coupling line 17 and the third filter coupling line 19, and the other end is grounded; one end of the second zero-point short-circuit line 22 is connected to the connection between the second filter coupling line 18 and the fourth filter coupling line 20, and the other end is grounded;

[0036] The two common-mode absorption resistors include a first common-mode absorption resistor 23 and a second common-mode absorption resistor 24; wherein one end of the first common-mode absorption resistor 23 is connected to the connection point between the first anti-connected wiring 13 and the second anti-connected wiring 14, and the other end is grounded; one end of the second common-mode absorption resistor 24 is connected to the connection point between the third anti-connected wiring 15 and the fourth anti-connected wiring 16, and the other end is grounded;

[0037] The two quarter-wavelength notch coupling lines include a first notch coupling line 25 and a second notch coupling line 26; the A port 5a of the first notch coupling line 25 is connected to the first notch absorption resistor 27; the B port 5b of the first notch coupling line 25 is connected to the third notch absorption resistor 29; the C port 5c and the D port 5d of the first notch coupling line 25 are both grounded; the A port 6a of the second notch coupling line 26 is connected to the second notch absorption resistor 28; the B port 6b of the second notch coupling line 26 is connected to the fourth notch absorption resistor 30; the C port 6c and the D port 6d of the second notch coupling line 26 are both grounded;

[0038] The four trap absorption resistors include a first trap absorption resistor 27, a second trap absorption resistor 28, a third trap absorption resistor 29 and a fourth trap absorption resistor 30; one end of the first trap absorption resistor 27 is connected to the C port 1c of the first filter coupling line 17, and the other end is connected to the A port 5a of the first trap coupling line 25; one end of the second trap absorption resistor 28 is connected to the C port 2c of the second filter coupling line 18, and the other end is connected to the A port 6a of the second trap coupling line 26; one end of the third trap absorption resistor 29 is connected to the C port 3c of the third filter coupling line 19, and the other end is connected to the B port 5b of the first trap coupling line 25; one end of the fourth trap absorption resistor 30 is connected to the C port 4c of the fourth filter coupling line 20, and the other end is connected to the B port 6b of the second trap coupling line 26;

[0039] The first non-reflection absorption branch 5, the second non-reflection absorption branch 6, the third non-reflection absorption branch 7 and the fourth non-reflection absorption branch 8 have the same structure; the first non-reflection absorption branch 5 includes a non-reflection absorption transmission line 51, a non-reflection absorption terminal open line 52 and a non-reflection absorption resistor 53; one end of the non-reflection absorption transmission line 51 is connected to the connection between the input port A+1 and the first signal transmission line 9, and the other end is connected to the B port 1b of the first filter coupling line 17; one end of the non-reflection absorption terminal open line 52 is connected to the connection between the non-reflection absorption transmission line 51 and the first filter coupling line 17, and the other end is open; one end of the non-reflection absorption resistor 53 is connected to the connection between the non-reflection absorption transmission line 51 and the first filter coupling line 17, and the other end is short-circuited.

[0040] The reflection-free characteristic of the out-of-band differential mode signal is adjusted by adjusting the first reflection-free absorption branch node 5 , the second reflection-free absorption branch node 6 , the third reflection-free absorption branch node 7 and the fourth reflection-free absorption branch node 8 .

[0041] The filtering characteristics of the differential mode signal are adjusted by adjusting the first filter coupling line 17 , the second filter coupling line 18 , the third filter coupling line 19 and the fourth filter coupling line 20 .

[0042] The out-of-band transmission zero point of the differential mode signal is adjusted by adjusting the first zero-point short-circuit line 21 and the second zero-point short-circuit line 22 .

[0043] The in-band suppression characteristics of the common-mode signal are adjusted by adjusting the first common-mode absorption resistor 23 and the second common-mode absorption resistor 24 .

[0044] The notch characteristics of the differential mode signal at the center frequency are adjusted by adjusting the first notch absorption resistor 27 , the second notch absorption resistor 28 , the third notch absorption resistor 29 and the fourth notch absorption resistor 30 .

[0045] Specific examples:

[0046] This example illustrates a broadband balanced notch filter with differential mode non-reflection characteristics. Figure 2 As shown, the broadband balanced notch filter with differential mode non-reflection characteristics described in the present invention introduces a deep notch with a first-order suppression effect better than -50dB at the center frequency 1GHz under differential mode signal excitation, which is used to eliminate the influence of in-band interference signals; the minimum differential mode transmission loss in the filter band |S ddBA | is -0.42dB, and the 3dB relative bandwidth is 63%. Four transmission zeros are introduced at 0GHz, 0.54GHz, 1.45GHz and 2GHz outside the filter band, so that the filter's out-of-band suppression capability is better than -20dB in the lower stopband of 0 to 0.6GHz and the upper stopband of 1.4 to 2GHz. The filter rectangular coefficient (30dB stopband bandwidth / 3dB passband bandwidth) is 1.36. The filter differential mode reflection coefficient |S ddAA | has 6 reflection zero points, located at 0.44GHz, 0.65GHz, 0.80GHz, 1.20GHz, 1.34GHz and 1.56GHz respectively; except near the notch frequency point, the differential mode reflection coefficient |S ddAA |In the frequency range of 0.34GHz to 1.66GHz, it is less than -10dB, and the differential mode non-reflection absorption bandwidth is 1.32 times the center frequency. Figure 3 As shown, the broadband balanced notch filter with differential mode non-reflection characteristics described in the present invention suppresses common mode transmission under common mode signal excitation. ccBA |In the frequency range of 0.55GHz to 1.44GHz, the difference is less than -20dB. This shows that the broadband balanced notch filter with differential mode non-reflection characteristics not only suppresses common mode noise but also realizes high selectivity filtering characteristics, good out-of-band suppression characteristics and out-of-band reflection signal absorption characteristics for differential mode signals.

[0047] In summary, the broadband balanced notch filter with differential mode non-reflection characteristics described in the present invention can effectively suppress common mode noise, and realizes a first-order deep notch at the center frequency of the balanced filter, good frequency selectivity and out-of-band suppression characteristics under the excitation of a differential mode signal, while also achieving effective absorption of differential mode out-of-band reflection signals, thereby achieving differential mode non-reflection performance expansion of the balanced filter. Therefore, it is very suitable for application in various balanced microwave systems to improve the overall performance of the system.

[0048] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A broadband balanced notch filter with differential mode non-reflection characteristics, characterized in that: include: Balanced differential input port A, balanced differential output port B, four sets of non-reflective absorption branches, four sections of quarter-wavelength signal transmission lines, four sections of quarter-wavelength anti-connected wiring, four sections of quarter-wavelength filter coupling lines, two sections of quarter-wavelength zero-point short-circuit lines, two common-mode absorption resistors, two sections of quarter-wavelength notch coupling lines and four notch absorption resistors; The balanced differential input port A includes an input port A+(1) and an input port A-(2); The balanced differential output port B includes an output port B+(3) and an output port B-(4); The four groups of non-reflection absorbing branches include a first non-reflection absorbing branch (5), a second non-reflection absorbing branch (6), a third non-reflection absorbing branch (7) and a fourth non-reflection absorbing branch (8); The four quarter-wavelength signal transmission lines include a first signal transmission line (9), a second signal transmission line (10), a third signal transmission line (11) and a fourth signal transmission line (12); wherein one end of the first signal transmission line (9) is connected to the input port A+(1), and the other end is connected to the connection point between the first anti-connecting line (13) and the first filter coupling line (17); one end of the second signal transmission line (10) is connected to the input port A-(2), and the other end is connected to the connection point between the second anti-connecting line (14) and the second filter coupling line (18); one end of the third signal transmission line (11) is connected to the output port B+(3), and the other end is connected to the connection point between the third anti-connecting line (15) and the third filter coupling line (19); one end of the fourth signal transmission line (12) is connected to the output port B-(4), and the other end is connected to the connection point between the fourth anti-connecting line (16) and the fourth filter coupling line (20); The four quarter-wavelength anti-connected wirings include a first anti-connected wiring (13), a second anti-connected wiring (14), a third anti-connected wiring (15) and a fourth anti-connected wiring (16); wherein one end of the first anti-connected wiring (13) is connected to the connection between the first signal transmission line (9) and the first filter coupling line (17), and the other end is connected to the second anti-connected wiring (14); one end of the second anti-connected wiring (14) is connected to the connection between the second signal transmission line (10) and the second filter coupling line (18), and the other end is connected to the first anti-connected wiring (13); one end of the third anti-connected wiring (15) is connected to the connection between the third signal transmission line (11) and the third filter coupling line (19), and the other end is connected to the fourth anti-connected wiring (16); one end of the fourth anti-connected wiring (16) is connected to the connection between the fourth signal transmission line (12) and the fourth filter coupling line (20), and the other end is connected to the third anti-connected wiring (15); The four quarter-wavelength filter coupling lines include a first filter coupling line (17), a second filter coupling line (18), a third filter coupling line (19) and a fourth filter coupling line (20); the A port (1a) of the first filter coupling line (17) is connected to the connection between the first signal transmission line (9) and the first anti-connection connection line (13); the A port (2a) of the second filter coupling line (18) is connected to the connection between the second signal transmission line (10) and the second anti-connection connection line (14); the A port (3a) of the third filter coupling line (19) is connected to the connection between the third signal transmission line (11) and the third anti-connection connection line (15); The A port (4a) of the fourth filter coupling line (20) is connected to the connection point between the fourth signal transmission line (12) and the fourth anti-connection line (16); the D port (1d) of the first filter coupling line (17) is connected to the D port (3d) of the third filter coupling line (19); and the D port (2d) of the second filter coupling line (18) is connected to the D port (4d) of the fourth filter coupling line (20); The two quarter-wavelength zero-point short-circuit lines include a first zero-point short-circuit line (21) and a second zero-point short-circuit line (22); wherein one end of the first zero-point short-circuit line (21) is connected to the connection point between the first filter coupling line (17) and the third filter coupling line (19), and the other end is grounded; and one end of the second zero-point short-circuit line (22) is connected to the connection point between the second filter coupling line (18) and the fourth filter coupling line (20), and the other end is grounded; The two common-mode absorption resistors include a first common-mode absorption resistor (23) and a second common-mode absorption resistor (24); wherein one end of the first common-mode absorption resistor (23) is connected to the connection point between the first anti-connecting wiring (13) and the second anti-connecting wiring (14), and the other end is grounded; and one end of the second common-mode absorption resistor (24) is connected to the connection point between the third anti-connecting wiring (15) and the fourth anti-connecting wiring (16), and the other end is grounded; The two quarter-wavelength notch coupling lines comprise a first notch coupling line (25) and a second notch coupling line (26); the A port (5a) of the first notch coupling line (25) is connected to a first notch absorption resistor (27); the B port (5b) of the first notch coupling line (25) is connected to a third notch absorption resistor (29); the C port (5c) and the D port (5d) of the first notch coupling line (25) are both grounded; the A port (6a) of the second notch coupling line (26) is connected to a second notch absorption resistor (28); the B port (6b) of the second notch coupling line (26) is connected to a fourth notch absorption resistor (30); the C port (6c) and the D port (6d) of the second notch coupling line (26) are both grounded; The four trap absorption resistors include a first trap absorption resistor (27), a second trap absorption resistor (28), a third trap absorption resistor (29) and a fourth trap absorption resistor (30); one end of the first trap absorption resistor (27) is connected to the C port (1c) of the first filter coupling line (17), and the other end is connected to the A port (5a) of the first trap coupling line (25); one end of the second trap absorption resistor (28) is connected to the C port (1c) of the second filter coupling line (18), and the other end is connected to the A port (5a) of the first trap coupling line (25); 2c), and the other end is connected to the A port (6a) of the second notch coupling line (26); one end of the third notch absorption resistor (29) is connected to the C port (3c) of the third filter coupling line (19), and the other end is connected to the B port (5b) of the first notch coupling line (25); one end of the fourth notch absorption resistor (30) is connected to the C port (4c) of the fourth filter coupling line (20), and the other end is connected to the B port (6b) of the second notch coupling line (26); The first non-reflection absorption branch (5), the second non-reflection absorption branch (6), the third non-reflection absorption branch (7) and the fourth non-reflection absorption branch (8) have the same structure; the first non-reflection absorption branch (5) comprises a non-reflection absorption transmission line (51), a non-reflection absorption terminal open line (52) and a non-reflection absorption resistor (53); one end of the non-reflection absorption transmission line (51) is connected to the connection between the input port A+ (1) and the first signal transmission line (9), and the other end is connected to the B port (1b) of the first filter coupling line (17); one end of the non-reflection absorption terminal open line (52) is connected to the connection between the non-reflection absorption transmission line (51) and the first filter coupling line (17), and the other end is open circuit; one end of the non-reflection absorption resistor (53) is connected to the connection between the non-reflection absorption transmission line (51) and the first filter coupling line (17), and the other end is short circuit.

2. A broadband balanced notch filter with differential mode non-reflection characteristics according to claim 1, characterized in that: The reflection-free characteristic of the out-of-band differential mode signal is adjusted by adjusting the first reflection-free absorption branch node (5), the second reflection-free absorption branch node (6), the third reflection-free absorption branch node (7) and the fourth reflection-free absorption branch node (8).

3. A broadband balanced notch filter with differential mode non-reflection characteristics according to claim 1, characterized in that: The filtering characteristics of the differential mode signal are adjusted by adjusting the first filtering coupling line (17), the second filtering coupling line (18), the third filtering coupling line (19) and the fourth filtering coupling line (20).

4. The broadband balanced notch filter with differential mode non-reflection characteristics according to claim 1, characterized in that: The out-of-band transmission zero point of the differential mode signal is adjusted by adjusting the first zero point short-circuit line (21) and the second zero point short-circuit line (22).

5. The broadband balanced notch filter with differential mode non-reflection characteristics according to claim 1, characterized in that: The in-band suppression characteristics of the common-mode signal are adjusted by adjusting the first common-mode absorption resistor (23) and the second common-mode absorption resistor (24).

6. A broadband balanced notch filter with differential mode non-reflection characteristics according to claim 1, characterized in that: The notch characteristics of the differential mode signal at the center frequency are adjusted by adjusting the first notch absorption resistor (27), the second notch absorption resistor (28), the third notch absorption resistor (29) and the fourth notch absorption resistor (30).

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