CN116995383A - Balanced linear phase band-pass filter with differential mode non-reflection characteristic - Google Patents
Balanced linear phase band-pass filter with differential mode non-reflection characteristic Download PDFInfo
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- H01P1/20—Frequency-selective devices, e.g. filters
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
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Abstract
The application discloses a balanced linear phase band-pass filter with a differential mode non-reflection characteristic, which comprises the following components: the device comprises a balance type differential input port A, a balance type differential output port B, a four-section quarter-wavelength impedance transformation line, a four-section quarter-wavelength microstrip transmission line, a four-section quarter-wavelength resonance microstrip line, two-section quarter-wavelength inversion transformation lines, four groups of reflection-free absorption branches, two groups of low-frequency negative group delay branches and two groups of high-frequency negative group delay branches. The balanced band-pass filter can be realized on a single PCB, has a simple structure and is beneficial to processing integration. Besides, the filter not only can effectively inhibit common-mode noise and improve the electromagnetic compatibility of a communication system, but also can effectively absorb out-of-band signals through resistors and reduce the reflection wave energy of the out-of-band signals, so that the differential mode non-reflection characteristic is realized, and meanwhile, the group delay fluctuation of the filter is reduced by loading the negative group delay branches, the linear phase band-pass filter characteristic is realized, and the overall performance of the balanced band-pass filter is further improved.
Description
Technical Field
The application relates to a balanced band-pass filter, in particular to a balanced linear phase band-pass filter with a differential mode reflection-free characteristic.
Background
In modern wireless communication systems, balanced circuits play an important role. Compared with an unbalanced single-port input/output circuit, the balanced circuit can efficiently suppress environmental noise and noise generated by an internal active device, and thus has excellent 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 need for balanced devices is becoming more stringent. The balanced filter has filtering characteristics when a differential mode signal is input, and can effectively inhibit common mode noise. The balanced filter can be simply constructed by one single-port filter and two balun, but its size is huge. Therefore, the design of the balance filter as a single device is very important without adding balun, and the balance filter has wide application prospect.
The conventional filter is a reflective filter, and the energy of the unwanted frequency components is reflected back to the signal source to achieve the purpose of filtering, so as to realize the frequency selectivity. In a nonlinear system, mixing a reflected echo signal with an existing signal will produce many interfering signals, thereby greatly affecting the performance of the system. In order to solve the negative effects of the conventional filter, an attenuator is generally cascaded in front of the conventional filter, and an amplifier is cascaded after the attenuator, so that the effects of the reflected wave signal of the conventional filter are eliminated to the greatest extent. The reflection-free filter can solve the problems of the conventional filter, can effectively absorb out-of-band signals through a resistor and then emit out the out-of-band signals in a heat form, and reduces the reflected wave energy of the out-of-band signals, so that the overall performance of the system is improved.
In measuring the performance of a transmission system, the frequency domain characteristic and the time domain characteristic of the system are usually analyzed at the same time, wherein the object to be analyzed of the frequency domain characteristic includes amplitude-frequency characteristic and phase-frequency characteristic. A good transmission system should have not only flat amplitude-frequency characteristics but also linear phase-frequency characteristics, i.e. flat group delay characteristics. With the continuous improvement of research and application of the negative group delay technology, the convex part of the filter group delay fluctuation curve can be compensated by utilizing an external equalization design mode through the negative group delay generated by the negative group delay circuit in a specific frequency band, without increasing the overall delay of the system, and the linear phase band-pass filter characteristic is realized.
However, most of the existing balanced filters still stay in researches on the aspects of widening filtering bandwidth, enhancing filtering selectivity, improving out-of-band rejection and common mode rejection capability of the filters, and the like, and few researches on balanced reflectionless filters or balanced linear phase filters are performed, so that the research on the balanced band-pass filters realizes the function expansion of reflectionless filtering and linear phase while realizing the common mode rejection characteristic has very important significance. In view of this, it is indeed necessary to propose a balanced linear phase bandpass filter with differential-mode non-reflection characteristics.
Disclosure of Invention
Based on the above, in order to solve the defects existing in the prior art, a balanced linear phase band-pass filter with a differential mode non-reflection characteristic is specially provided.
Based on the above object, the technical scheme of the present application comprises: the device comprises a balance type differential input port A, a balance type differential output port B, a four-section quarter-wavelength impedance transformation line, a four-section quarter-wavelength microstrip transmission line, a four-section quarter-wavelength resonance microstrip line, two-section quarter-wavelength inversion transformation lines, four groups of reflection-free absorption branches, two groups of low-frequency negative group delay branches and two groups of high-frequency negative group delay branches;
the balanced differential input port A comprises an input port A+ and an input port A-;
the balanced differential output port B comprises an output port B+ and an output port B-;
the four-segment quarter-wavelength impedance transformation line comprises a first impedance transformation line, a second impedance transformation line, a third impedance transformation line and a fourth impedance transformation line; one end of the first impedance transformation line is connected with the input port A+ and the other end of the first impedance transformation line is connected with the first microstrip transmission line; one end of the second impedance transformation line is connected with the input port A-and the other end of the second impedance transformation line is connected with the second microstrip transmission line; one end of the third impedance transformation line is connected with the output port B+ and the other end of the third impedance transformation line is connected with a third microstrip transmission line; one end of the fourth impedance transformation line is connected with the output port B-and the other end of the fourth impedance transformation line is connected with a fourth microstrip transmission line;
the four-section quarter-wavelength microstrip transmission line comprises a first microstrip transmission line, a second microstrip transmission line, a third microstrip transmission line and a fourth microstrip transmission line; one end of the first microstrip transmission line is connected with the first impedance transformation line, and the other end of the first microstrip transmission line is connected with the connection part of the first resonance microstrip line and the first inversion transformation line; one end of the second microstrip transmission line is connected with the second impedance transformation line, and the other end of the second microstrip transmission line is connected with the connection part of the second resonance microstrip line and the second inversion transformation line; one end of the third microstrip transmission line is connected with the third impedance transformation line, and the other end of the third microstrip transmission line is connected with the connection part of the third resonance microstrip line and the first inversion transformation line; one end of the fourth microstrip transmission line is connected with the fourth impedance transformation line, and the other end of the fourth microstrip transmission line is connected with the connection part of the fourth resonance microstrip line and the second inversion transformation line;
the four-section quarter-wavelength resonant microstrip line comprises a first resonant microstrip line, a second resonant microstrip line, a third resonant microstrip line and a fourth resonant microstrip line; one end of the first resonant microstrip line is connected with the second resonant microstrip line, and the other end of the first resonant microstrip line is connected with the connection part of the first microstrip transmission line and the first inversion conversion line; one end of the second resonance microstrip line is connected with the first resonance microstrip line, and the other end of the second resonance microstrip line is connected with the connection part of the second microstrip transmission line and the second inversion conversion line; one end of the third resonance microstrip line is connected with the fourth resonance microstrip line, and the other end of the third resonance microstrip line is connected with the connection part of the third microstrip transmission line and the first inversion conversion line; one end of the fourth resonance microstrip line is connected with the third resonance microstrip line, and the other end of the fourth resonance microstrip line is connected with the connection part of the fourth microstrip transmission line and the second inversion conversion line;
the two sections of quarter-wavelength inversion conversion lines comprise a first inversion conversion line and a second inversion conversion line; one end of the first inversion conversion line is connected to the connection part of the first microstrip transmission line and the first resonance microstrip line, and the other end of the first inversion conversion line is connected to the connection part of the third microstrip transmission line and the third resonance microstrip line; one end of the second inversion conversion line is connected to the connection part of the second microstrip transmission line and the second resonance microstrip line, and the other end of the second inversion conversion line is connected to the connection part of the fourth microstrip transmission line and the fourth resonance microstrip line;
the four groups of non-reflection absorption branches comprise a first non-reflection absorption branch, a second non-reflection absorption branch, a third non-reflection absorption branch and a fourth non-reflection absorption branch; the first non-reflection absorption branch is connected to the connection part of the first impedance transformation line and the first microstrip transmission line; the second reflection-free absorption branch is connected to the connection part of the second impedance transformation line and the second microstrip transmission line; the third reflection-free absorption branch is connected to the joint of the third impedance transformation line and the first microstrip transmission line; the fourth reflection-free absorption branch is connected to the joint of the fourth impedance transformation line and the fourth microstrip transmission line;
the first non-reflection absorption branch, the second non-reflection absorption branch, the third non-reflection absorption branch and the fourth non-reflection absorption branch have the same structure; the first non-reflection absorption branch comprises a non-reflection absorption transmission line, a non-reflection absorption open-circuit branch and a non-reflection absorption resistor; one end of the non-reflection absorption transmission line is connected to the connection part of the first impedance transformation line and the first microstrip transmission line, and the other end of the non-reflection absorption transmission line is connected to the connection part of the non-reflection absorption open-circuit branch and the non-reflection absorption resistor; one end of the reflection-free absorption open circuit branch is connected to the joint of the reflection-free absorption transmission line and the reflection-free absorption resistor, and the other end of the reflection-free absorption open circuit branch is open; one end of the non-reflection absorption resistor is connected to the connection part of the non-reflection absorption transmission line and the non-reflection absorption open-circuit branch, and the other end of the non-reflection absorption resistor is grounded;
the two groups of low-frequency negative group delay branches comprise a first low-frequency negative group delay branch and a second low-frequency negative group delay branch; the first low-frequency negative group delay branch is connected to the joint of the first impedance transformation line and the first microstrip transmission line; the second low-frequency negative group delay branch is connected to the joint of the second impedance transformation line and the second microstrip transmission line;
the first low-frequency negative group delay branch and the second low-frequency negative group delay branch have the same structure; the first low-frequency negative group delay branch comprises a low-frequency negative group delay transmission line, a low-frequency negative group delay short circuit branch and a low-frequency negative group delay absorption resistor; one end of the low-frequency negative group delay transmission line is connected to the connection part of the first impedance transformation line and the first microstrip transmission line, and the other end of the low-frequency negative group delay transmission line is connected to the connection part of the low-frequency negative group delay short circuit branch and the low-frequency negative group delay absorption resistor; one end of the low-frequency negative group delay short circuit branch is connected to the connection part of the low-frequency negative group delay transmission line and the low-frequency negative group delay absorption resistor, and the other end of the low-frequency negative group delay short circuit branch is grounded; one end of the low-frequency negative group delay absorption resistor is connected to the connection part of the low-frequency negative group delay transmission line and the low-frequency negative group delay short circuit branch, and the other end of the low-frequency negative group delay absorption resistor is grounded;
the two groups of high-frequency negative group delay branches comprise a first high-frequency negative group delay branch and a second high-frequency negative group delay branch; the first high-frequency negative group delay branch is connected to the joint of the third impedance transformation line and the third microstrip transmission line; the second high-frequency negative group delay branch is connected to the joint of the fourth impedance transformation line and the fourth microstrip transmission line;
the first high-frequency negative group delay branch and the second high-frequency negative group delay branch have the same structure; the first high-frequency negative group delay branch comprises a high-frequency negative group delay transmission line, a high-frequency negative group delay short circuit branch and a high-frequency negative group delay absorption resistor; one end of the high-frequency negative group delay transmission line is connected to the connection part of the third impedance transformation line and the third microstrip transmission line, and the other end of the high-frequency negative group delay transmission line is connected to the connection part of the high-frequency negative group delay short circuit branch and the high-frequency negative group delay absorption resistor; one end of the high-frequency negative group delay short circuit branch is connected to the connection part of the high-frequency negative group delay transmission line and the high-frequency negative group delay absorption resistor, and the other end of the high-frequency negative group delay short circuit branch is grounded; one end of the high-frequency negative group delay absorption resistor is connected to the connection part of the high-frequency negative group delay transmission line and the high-frequency negative group delay short circuit branch, and the other end of the high-frequency negative group delay absorption resistor is grounded.
Further, the matching characteristics of the band-pass filter under the excitation of the differential mode signal are adjusted by adjusting the first impedance transformation line, the second impedance transformation line, the third impedance transformation line and the fourth impedance transformation line.
Further, the filtering characteristic of the band-pass filter under the excitation of the differential mode signal is adjusted by adjusting the first resonant microstrip line, the second resonant microstrip line, the third resonant microstrip line and the fourth resonant microstrip line.
Further, the non-reflection absorption characteristics of the band-pass filter are adjusted by adjusting the first non-reflection absorption branch, the second non-reflection absorption branch, the third non-reflection absorption branch, and the fourth non-reflection absorption branch.
Further, the group delay fluctuation value at the low frequency band in the passband of the band-pass filter is reduced by adjusting the first low frequency negative group delay branch and the second low frequency negative group delay branch.
Further, the group delay fluctuation value at the high frequency band in the passband of the band-pass filter is reduced by adjusting the first high frequency negative group delay branch and the second high frequency negative group delay branch.
Compared with the prior art, the balanced linear phase band-pass filter with the differential mode non-reflection characteristic has the following beneficial effects: in order to design a balanced filter as a single device and make up for the defects of the current research on the function expansion aspects of the balanced filter such as no reflection characteristic, linear phase characteristic and the like, the application provides a balanced linear phase band-pass filter with a differential mode no reflection characteristic. The balanced band-pass filter can be realized on a single PCB, has a simple structure and is beneficial to processing integration. Besides, the filter not only can effectively inhibit common-mode noise and improve the electromagnetic compatibility of a communication system, but also can effectively absorb out-of-band signals through resistors and reduce the reflection wave energy of the out-of-band signals, so that the differential mode non-reflection characteristic is realized, and meanwhile, the group delay fluctuation of the filter is reduced by loading the negative group delay branches, the linear phase band-pass filter characteristic is realized, and the overall performance of the balanced band-pass filter is further improved.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present application, and other drawings may be obtained according to the drawings without inventive effort to those skilled in the art.
FIG. 1 is a schematic diagram of a balanced linear phase bandpass filter with differential mode non-reflection characteristics according to the application;
FIG. 2 is a graph of the magnitude of a hybrid S-parameter of a balanced linear phase bandpass filter with differential-mode non-reflection characteristics of the present application under differential-mode signal excitation;
FIG. 3 is a graph of the magnitude of a mixed S-parameter of a balanced linear phase bandpass filter with differential mode non-reflection characteristics of the present application under common mode signal excitation;
FIG. 4 is a graph comparing group delay curves of a balanced linear phase bandpass filter with differential mode non-reflection characteristic loaded negative group delay branches and unloaded negative group delay branches.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
The application relates to a balanced linear phase band-pass filter with a differential mode non-reflection characteristic, which is characterized by comprising the following components: the device comprises a balance type differential input port A, a balance type differential output port B, a four-section quarter-wavelength impedance transformation line, a four-section quarter-wavelength microstrip transmission line, a four-section quarter-wavelength resonance microstrip line, two-section quarter-wavelength inversion transformation lines, four groups of reflection-free absorption branches, two groups of low-frequency negative group delay branches and two groups of high-frequency negative group delay branches;
the balanced differential input port A comprises an input port A+1 and an input port A-2;
the balanced differential output port B comprises an output port B+3 and an output port B-4;
the four-segment quarter-wavelength impedance transformation line comprises a first impedance transformation line 5, a second impedance transformation line 6, a third impedance transformation line 7 and a fourth impedance transformation line 8; wherein one end of the first impedance transformation line 5 is connected with the input port A+1, and the other end is connected with the first microstrip transmission line 9; one end of the second impedance transformation line 6 is connected with the input port A-2, and the other end is connected with the second microstrip transmission line 10; one end of the third impedance transformation line 7 is connected with the output port B+3, and the other end of the third impedance transformation line is connected with the third microstrip transmission line 11; one end of the fourth impedance transformation line 8 is connected with the output port B-4, and the other end of the fourth impedance transformation line is connected with the fourth microstrip transmission line 12;
the four-section quarter-wavelength microstrip transmission line comprises a first microstrip transmission line 9, a second microstrip transmission line 10, a third microstrip transmission line 11 and a fourth microstrip transmission line 12; wherein one end of the first microstrip transmission line 9 is connected with the first impedance transformation line 5, and the other end is connected with the connection part of the first resonance microstrip line 13 and the first inversion transformation line 17; one end of the second microstrip transmission line 10 is connected with the second impedance transformation line 6, and the other end is connected with the connection part of the second resonance microstrip line 14 and the second inversion transformation line 18; one end of the third microstrip transmission line 11 is connected with the third impedance transformation line 7, and the other end is connected with the connection part of the third resonance microstrip line 15 and the first inversion transformation line 17; one end of the fourth microstrip transmission line 12 is connected with the fourth impedance transformation line 8, and the other end is connected with the connection part of the fourth resonance microstrip line 16 and the second inversion transformation line 18;
the four-section quarter-wavelength resonant microstrip line comprises a first resonant microstrip line 13, a second resonant microstrip line 14, a third resonant microstrip line 15 and a fourth resonant microstrip line 16; wherein one end of the first resonant microstrip line 13 is connected with the second resonant microstrip line 14, and the other end is connected with the connection part of the first microstrip transmission line 9 and the first inversion conversion line 17; one end of the second resonant microstrip line 14 is connected with the first resonant microstrip line 13, and the other end of the second resonant microstrip line is connected with the connection part of the second microstrip transmission line 10 and the second inversion conversion line 18; one end of the third resonant microstrip line 15 is connected with the fourth resonant microstrip line 16, and the other end of the third resonant microstrip line is connected with the connection part of the third microstrip transmission line 11 and the first inversion conversion line 17; one end of the fourth resonant microstrip line 16 is connected with the third resonant microstrip line 15, and the other end is connected with the connection part of the fourth microstrip transmission line 12 and the second inversion conversion line 18;
the two segments of quarter-wavelength inversion transformation lines comprise a first inversion transformation line 17 and a second inversion transformation line 18; one end of the first inversion transformation line 17 is connected to the connection position of the first microstrip transmission line 9 and the first resonance microstrip line 13, and the other end is connected to the connection position of the third microstrip transmission line 11 and the third resonance microstrip line 15; one end of the second inversion transformation line 18 is connected to the connection between the second microstrip transmission line 10 and the second resonant microstrip line 14, and the other end is connected to the connection between the fourth microstrip transmission line 12 and the fourth resonant microstrip line 16;
the four groups of non-reflective absorbing branches comprise a first non-reflective absorbing branch 19, a second non-reflective absorbing branch 20, a third non-reflective absorbing branch 21 and a fourth non-reflective absorbing branch 22; wherein the first non-reflection absorption branch 19 is connected to the connection part of the first impedance transformation line 5 and the first microstrip transmission line 9; the second reflection-free absorption branch 20 is connected to the connection part of the second impedance transformation line 6 and the second microstrip transmission line 10; the third reflection-free absorption branch 21 is connected to the connection part of the third impedance transformation line 7 and the first microstrip transmission line 11; the fourth reflection-free absorption branch 22 is connected to the connection part of the fourth impedance transformation line 8 and the fourth microstrip transmission line 12;
the first non-reflection absorbing branch 19, the second non-reflection absorbing branch 20, the third non-reflection absorbing branch 21 and the fourth non-reflection absorbing branch 22 have the same structure; the first non-reflective absorbing branch includes a non-reflective absorbing transmission line 191, a non-reflective absorbing open branch 192, and a non-reflective absorbing resistor 193; wherein one end of the non-reflection absorption transmission line 191 is connected to the connection between the first impedance transformation line 5 and the first microstrip transmission line 9, and the other end is connected to the connection between the non-reflection absorption open branch 192 and the non-reflection absorption resistor 193; one end of the non-reflection absorption open circuit branch 192 is connected to the connection part of the non-reflection absorption transmission line 191 and the non-reflection absorption resistor 193, and the other end is open circuit; one end of the non-reflection absorption resistor 193 is connected to the connection part of the non-reflection absorption transmission line 191 and the non-reflection absorption open circuit branch 192, and the other end is grounded;
the two groups of low-frequency negative group delay branches comprise a first low-frequency negative group delay branch 23 and a second low-frequency negative group delay branch 24; wherein the first low-frequency negative group delay branch 23 is connected to the connection part of the first impedance transformation line 5 and the first microstrip transmission line 9; the second low-frequency negative group delay branch 24 is connected to the connection part of the second impedance transformation line 6 and the second microstrip transmission line 10;
the first low-frequency negative group delay branch 23 and the second low-frequency negative group delay branch 24 have the same structure; the first low-frequency negative group delay branch 23 comprises a low-frequency negative group delay transmission line 231, a low-frequency negative group delay short circuit branch 232 and a low-frequency negative group delay absorption resistor 233; one end of the low-frequency negative group delay transmission line 231 is connected to the connection between the first impedance transformation line 5 and the first microstrip transmission line 9, and the other end is connected to the connection between the low-frequency negative group delay short-circuit branch 232 and the low-frequency negative group delay absorption resistor 233; one end of the low-frequency negative group delay short circuit branch 232 is connected to the connection part of the low-frequency negative group delay transmission line 231 and the low-frequency negative group delay absorption resistor 233, and the other end is grounded; one end of the low-frequency negative group delay absorbing resistor 233 is connected to the connection part of the low-frequency negative group delay transmission line 231 and the low-frequency negative group delay short circuit branch 232, and the other end is grounded;
the two groups of high-frequency negative group delay branches comprise a first high-frequency negative group delay branch 25 and a second high-frequency negative group delay branch 26; wherein the first high-frequency negative group delay branch 25 is connected to the connection part of the third impedance transformation line 7 and the third microstrip transmission line 11; the second high-frequency negative group delay branch 26 is connected to the connection part of the fourth impedance transformation line 8 and the fourth microstrip transmission line 12;
the first high-frequency negative group delay branch 25 and the second high-frequency negative group delay branch 26 have the same structure; the first high-frequency negative group delay branch 25 comprises a high-frequency negative group delay transmission line 251, a high-frequency negative group delay short circuit branch 252 and a high-frequency negative group delay absorption resistor 253; one end of the high-frequency negative group delay transmission line 251 is connected to the connection between the third impedance transformation line 7 and the third microstrip transmission line 11, and the other end is connected to the connection between the high-frequency negative group delay short circuit branch 252 and the high-frequency negative group delay absorbing resistor 253; one end of the high-frequency negative group delay short circuit branch 252 is connected to the connection part of the high-frequency negative group delay transmission line 251 and the high-frequency negative group delay absorption resistor 253, and the other end is grounded; one end of the high-frequency negative group delay absorbing resistor 253 is connected to the connection part of the high-frequency negative group delay transmission line 251 and the high-frequency negative group delay short circuit branch 252, and the other end is grounded.
Further, the matching characteristics of the band-pass filter under the excitation of the differential mode signal are adjusted by adjusting the first impedance transformation line 5, the second impedance transformation line 6, the third impedance transformation line 7, and the fourth impedance transformation line 8.
Further, the filtering characteristics of the band-pass filter under the excitation of the differential mode signal are adjusted by adjusting the first resonant microstrip line 13, the second resonant microstrip line 14, the third resonant microstrip line 15 and the fourth resonant microstrip line 16.
Further, the non-reflection absorption characteristics of the band-pass filter are adjusted by adjusting the first non-reflection absorption branch 19, the second non-reflection absorption branch 20, the third non-reflection absorption branch 21, and the fourth non-reflection absorption branch 22.
Further, the group delay variation value at the low frequency band in the passband of the bandpass filter is reduced by adjusting the first low frequency negative group delay branch 23 and the second low frequency negative group delay branch 24.
Further, the group delay variation value at the high frequency band in the passband of the bandpass filter is reduced by adjusting the first high frequency negative group delay branch 25 and the second high frequency negative group delay branch 26.
In order to further describe the balanced linear phase bandpass filter with differential mode non-reflection characteristic provided by the application, the following specific examples are implemented on the premise of the technical scheme of the application, but the protection scope of the application is not limited to the following examples, and the methods used in the following examples are conventional methods unless otherwise specified.
Specific examples: this example illustrates a balanced linear phase bandpass filter with differential mode non-reflective characteristics. As shown in FIG. 2, a balanced linear phase bandpass filter with differential-mode non-reflection characteristics according to the application has an input port reflection coefficient |S at a center frequency of 2.45GHz under differential-mode signal excitation ddAA I is-24.4 dB, and the reflection coefficient of the output port is S ddBB I is-22.4 dB; differential mode transmission coefficient |S at center frequency ddBA The I is-1.63 dB, and the 3dB differential mode transmission bandwidth is 850MHz; input differential mode reflection coefficient |S ddAA The I is smaller than-10 dB in the frequency range of 0.87-3.76 GHz, and the input end differential mode non-reflection absorption bandwidth is 3.40 times of the 3dB differential mode transmission bandwidth; output differential mode reflection coefficient |S ddBB The I is smaller than-10 dB in the frequency range of 0.91-3.89 GHz, the differential mode non-reflection absorption bandwidth of the output end is 3.51 times of the 3dB differential mode transmission bandwidth, and the broadband differential mode non-reflection characteristic is achieved. As shown in fig. 3, a balanced linear phase bandpass filter with differential-mode non-reflection characteristic according to the application suppresses |s in common-mode transmission under common-mode signal excitation ccBA The I is smaller than-20 dB in the frequency range of 1.77-3.11 GHz, and the common mode rejection bandwidth is 1.58 times of the 3dB differential mode transmission bandwidth. As shown in fig. 4, the group delay fluctuation in the passband of the balanced linear phase bandpass filter with the characteristic of differential mode no reflection when loading negative group delay branches is less than 0.15ns. The balanced linear phase band-pass filter with the differential mode non-reflection characteristic not only inhibits common mode noise and realizes non-reflection absorption outside a differential mode signal passband, but also compensates a convex part of a filter group delay fluctuation curve and realizes linear phase band-pass filtering characteristic.
In summary, the balanced linear phase band-pass filter with the differential mode non-reflection characteristic can effectively inhibit common mode noise, has excellent electromagnetic compatibility, can effectively absorb out-of-band signals through resistors, reduces reflected wave energy of the out-of-band signals, achieves broadband differential mode non-reflection characteristic, and simultaneously reduces filter group delay fluctuation by loading negative group delay branches, and achieves linear phase band-pass filtering characteristic. In addition, the balanced linear phase band-pass filter with the differential mode non-reflection characteristic can be realized on a single PCB, has a simple structure, is beneficial to processing and integration, and is very suitable for various balanced microwave systems to improve the overall performance of the system.
The foregoing is only a preferred embodiment of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art, who is within the scope of the present application, should make equivalent substitutions or modifications according to the technical scheme of the present application and the inventive concept thereof, and should be covered by the scope of the present application.
Claims (6)
1. A balanced linear phase bandpass filter having differential-mode non-reflective characteristics, comprising: the device comprises a balance type differential input port A, a balance type differential output port B, a four-section quarter-wavelength impedance transformation line, a four-section quarter-wavelength microstrip transmission line, a four-section quarter-wavelength resonance microstrip line, two-section quarter-wavelength inversion transformation lines, four groups of reflection-free absorption branches, two groups of low-frequency negative group delay branches and two groups of high-frequency negative group delay branches;
the balanced differential input port A comprises an input port A+ (1) and an input port A- (2);
the balanced differential output port B comprises an output port B+ (3) and an output port B- (4);
the four-segment quarter-wavelength impedance transformation line comprises a first impedance transformation line (5), a second impedance transformation line (6), a third impedance transformation line (7) and a fourth impedance transformation line (8); one end of the first impedance transformation line (5) is connected with the input port A+ (1), and the other end of the first impedance transformation line is connected with the first microstrip transmission line (9); one end of the second impedance transformation line (6) is connected with the input port A- (2), and the other end of the second impedance transformation line is connected with the second microstrip transmission line (10); one end of the third impedance transformation line (7) is connected with the output port B+ (3), and the other end of the third impedance transformation line is connected with the third microstrip transmission line (11); one end of the fourth impedance transformation line (8) is connected with the output port B- (4), and the other end of the fourth impedance transformation line is connected with the fourth microstrip transmission line (12);
the four-section quarter-wavelength microstrip transmission line comprises a first microstrip transmission line (9), a second microstrip transmission line (10), a third microstrip transmission line (11) and a fourth microstrip transmission line (12); one end of the first microstrip transmission line (9) is connected with the first impedance transformation line (5), and the other end of the first microstrip transmission line is connected with the connection part of the first resonance microstrip line (13) and the first inversion transformation line (17); one end of the second microstrip transmission line (10) is connected with the second impedance transformation line (6), and the other end of the second microstrip transmission line is connected with the connection part of the second resonance microstrip line (14) and the second inversion transformation line (18); one end of the third microstrip transmission line (11) is connected with the third impedance transformation line (7), and the other end of the third microstrip transmission line is connected with the connection part of the third resonance microstrip line (15) and the first inversion transformation line (17); one end of the fourth microstrip transmission line (12) is connected with the fourth impedance transformation line (8), and the other end of the fourth microstrip transmission line is connected with the connection part of the fourth resonance microstrip line (16) and the second inversion transformation line (18);
the four-section quarter-wavelength resonant microstrip line comprises a first resonant microstrip line (13), a second resonant microstrip line (14), a third resonant microstrip line (15) and a fourth resonant microstrip line (16); one end of the first resonance microstrip line (13) is connected with the second resonance microstrip line (14), and the other end of the first resonance microstrip line is connected with the connection part of the first microstrip transmission line (9) and the first inversion conversion line (17); one end of the second resonance microstrip line (14) is connected with the first resonance microstrip line (13), and the other end of the second resonance microstrip line is connected with the connection part of the second microstrip transmission line (10) and the second inversion conversion line (18); one end of the third resonance microstrip line (15) is connected with the fourth resonance microstrip line (16), and the other end of the third resonance microstrip line is connected with the connection part of the third microstrip transmission line (11) and the first inversion conversion line (17); one end of the fourth resonance microstrip line (16) is connected with the third resonance microstrip line (15), and the other end of the fourth resonance microstrip line is connected with the connection part of the fourth microstrip transmission line (12) and the second inversion conversion line (18);
the two segments of quarter-wavelength inversion transformation lines comprise a first inversion transformation line (17) and a second inversion transformation line (18); one end of the first inversion conversion line (17) is connected to the connection part of the first microstrip transmission line (9) and the first resonance microstrip line (13), and the other end of the first inversion conversion line is connected to the connection part of the third microstrip transmission line (11) and the third resonance microstrip line (15); one end of the second inversion conversion line (18) is connected to the connection part of the second microstrip transmission line (10) and the second resonance microstrip line (14), and the other end is connected to the connection part of the fourth microstrip transmission line (12) and the fourth resonance microstrip line (16);
the four groups of non-reflection absorption branches comprise a first non-reflection absorption branch (19), a second non-reflection absorption branch (20), a third non-reflection absorption branch (21) and a fourth non-reflection absorption branch (22); wherein the first non-reflection absorption branch (19) is connected to the connection part of the first impedance transformation line (5) and the first microstrip transmission line (9); the second reflection-free absorption branch (20) is connected to the joint of the second impedance transformation line (6) and the second microstrip transmission line (10); the third reflection-free absorption branch (21) is connected to the joint of the third impedance transformation line (7) and the first microstrip transmission line (11); the fourth reflection-free absorption branch (22) is connected to the joint of the fourth impedance transformation line (8) and the fourth microstrip transmission line (12);
the first non-reflection absorption branch (19), the second non-reflection absorption branch (20), the third non-reflection absorption branch (21) and the fourth non-reflection absorption branch (22) have the same structure; the first non-reflective absorbing branch comprises a non-reflective absorbing transmission line (191), a non-reflective absorbing open-circuit branch (192) and a non-reflective absorbing resistor (193); one end of the non-reflection absorption transmission line (191) is connected to the connection part of the first impedance transformation line (5) and the first microstrip transmission line (9), and the other end of the non-reflection absorption transmission line is connected to the connection part of the non-reflection absorption open branch (192) and the non-reflection absorption resistor (193); one end of the non-reflection absorption open circuit branch (192) is connected to the joint of the non-reflection absorption transmission line (191) and the non-reflection absorption resistor (193), and the other end is open circuit; one end of the non-reflection absorption resistor (193) is connected to the connection part of the non-reflection absorption transmission line (191) and the non-reflection absorption open branch (192), and the other end of the non-reflection absorption resistor is grounded;
the two groups of low-frequency negative group delay branches comprise a first low-frequency negative group delay branch (23) and a second low-frequency negative group delay branch (24); the first low-frequency negative group delay branch (23) is connected to the joint of the first impedance transformation line (5) and the first microstrip transmission line (9); the second low-frequency negative group delay branch (24) is connected to the joint of the second impedance transformation line (6) and the second microstrip transmission line (10);
the first low-frequency negative group delay branch (23) and the second low-frequency negative group delay branch (24) have the same structure; the first low-frequency negative group delay branch (23) comprises a low-frequency negative group delay transmission line (231), a low-frequency negative group delay short circuit branch (232) and a low-frequency negative group delay absorption resistor (233); one end of the low-frequency negative group delay transmission line (231) is connected to the connection part of the first impedance transformation line (5) and the first microstrip transmission line (9), and the other end of the low-frequency negative group delay transmission line is connected to the connection part of the low-frequency negative group delay short circuit branch (232) and the low-frequency negative group delay absorption resistor (233); one end of the low-frequency negative group delay short circuit branch (232) is connected to the connection part of the low-frequency negative group delay transmission line (231) and the low-frequency negative group delay absorption resistor (233), and the other end of the low-frequency negative group delay short circuit branch is grounded; one end of the low-frequency negative group delay absorption resistor (233) is connected to the joint of the low-frequency negative group delay transmission line (231) and the low-frequency negative group delay short-circuit branch (232), and the other end of the low-frequency negative group delay absorption resistor is grounded;
the two groups of high-frequency negative group delay branches comprise a first high-frequency negative group delay branch (25) and a second high-frequency negative group delay branch (26); wherein the first high-frequency negative group delay branch (25) is connected to the joint of the third impedance transformation line (7) and the third microstrip transmission line (11); the second high-frequency negative group delay branch (26) is connected to the joint of the fourth impedance transformation line (8) and the fourth microstrip transmission line (12);
the first high-frequency negative group delay branch (25) and the second high-frequency negative group delay branch (26) have the same structure; the first high-frequency negative group delay branch (25) comprises a high-frequency negative group delay transmission line (251), a high-frequency negative group delay short circuit branch (252) and a high-frequency negative group delay absorption resistor (253); one end of the high-frequency negative group delay transmission line (251) is connected to the connection part of the third impedance transformation line (7) and the third microstrip transmission line (11), and the other end of the high-frequency negative group delay transmission line is connected to the connection part of the high-frequency negative group delay short circuit branch (252) and the high-frequency negative group delay absorption resistor (253); one end of the high-frequency negative group delay short circuit branch (252) is connected to the connection part of the high-frequency negative group delay transmission line (251) and the high-frequency negative group delay absorption resistor (253), and the other end of the high-frequency negative group delay short circuit branch is grounded; one end of the high-frequency negative group delay absorption resistor (253) is connected to the connection part of the high-frequency negative group delay transmission line (251) and the high-frequency negative group delay short circuit branch (252), and the other end of the high-frequency negative group delay absorption resistor is grounded.
2. A balanced linear phase bandpass filter with differential-mode non-reflection characteristics according to claim 1, characterized in that: the matching characteristics of the band-pass filter under the excitation of a differential mode signal are adjusted by adjusting the first impedance transformation line (5), the second impedance transformation line (6), the third impedance transformation line (7) and the fourth impedance transformation line (8).
3. A balanced linear phase bandpass filter with differential-mode non-reflection characteristics according to claim 1, characterized in that: the filtering characteristics of the band-pass filter under the excitation of differential mode signals are adjusted by adjusting the first resonant microstrip line (13), the second resonant microstrip line (14), the third resonant microstrip line (15) and the fourth resonant microstrip line (16).
4. A balanced linear phase bandpass filter with differential-mode non-reflection characteristics according to claim 1, characterized in that: the non-reflection absorption characteristics of the band-pass filter are adjusted by adjusting the first non-reflection absorption branch (19), the second non-reflection absorption branch (20), the third non-reflection absorption branch (21) and the fourth non-reflection absorption branch (22).
5. A balanced linear phase bandpass filter with differential-mode non-reflection characteristics according to claim 1, characterized in that: the group delay fluctuation value at the low frequency band in the passband of the band-pass filter is reduced by adjusting the first low frequency negative group delay branch (23) and the second low frequency negative group delay branch (24).
6. A balanced linear phase bandpass filter with differential-mode non-reflection characteristics according to claim 1, characterized in that: the group delay fluctuation value at the high frequency band in the passband of the band-pass filter is reduced by adjusting the first high frequency negative group delay branch (25) and the second high frequency negative group delay branch (26).
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117375573A (en) * | 2023-12-07 | 2024-01-09 | 华南理工大学 | Reflection-free acoustic wave filter unit, reflection-free acoustic wave filter and manufacturing method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117375573A (en) * | 2023-12-07 | 2024-01-09 | 华南理工大学 | Reflection-free acoustic wave filter unit, reflection-free acoustic wave filter and manufacturing method |
| CN117375573B (en) * | 2023-12-07 | 2024-04-12 | 华南理工大学 | Reflection-free acoustic wave filter unit, reflection-free acoustic wave filter and manufacturing method |
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