A topology, low pass filter and communication device

Abstract

The embodiment of the present application relates to the technical field of communication, and discloses a kind of topology, low-pass filter and communication device, and the topology includes input end, output end, first microstrip line, second microstrip line, third microstrip line, fourth microstrip line, fifth microstrip line, first open stub, second open stub, third open stub, fourth open stub and fifth open stub.The one end of fourth microstrip line is connected with the one end of first microstrip line, second microstrip line and fifth microstrip line, the other end of first microstrip line is connected with input end and the one end of first open stub, the other end of second microstrip line is connected with output end and the one end of third microstrip line, the other end of third microstrip line is connected with second open stub, the other end of fifth microstrip line is connected with fifth open stub, and the other end of fourth microstrip line is connected with the one end of third open stub and fourth open stub.The above structure is used to design low-pass filter, and has the advantages of simple structure, high selectivity, high isolation and wide stopband.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the technical field of communication, in particular to a topology, a low-pass filter and a communication device. BACKGROUND

[0002] With the rapid development of the fifth generation mobile communication technology, people have higher requirements on the size and performance of electronic devices, and filters play an important role in communication systems to filter out noise, interference and other unwanted signals. Today's low-pass filters mainly have defect ground structure, step impedance resonator, stub-loaded resonator and sector resonator.

[0003] In the process of implementing the embodiments of the present application, the inventors found that the defect ground structure is composed of a double-layer circuit, the scheme based on the sector resonator needs multiple resonators in cascade, and the assembly is complex; the schemes based on the step impedance resonator and the stub-loaded resonator have the problems of narrow stopband or unsteep sideband. SUMMARY

[0004] In view of the above problems, embodiments of the present application provide a topology, a low-pass filter and a communication device, which overcome the above problems or at least partially solve the above problems.

[0005] To solve the above technical problems, one technical solution adopted by the present application is to provide a topology, which includes an input end, an output end, a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a fifth microstrip line, a first open-circuit stub, a second open-circuit stub, a third open-circuit stub, a fourth open-circuit stub and a fifth open-circuit stub. One end of the fourth microstrip line is connected to one end of the first microstrip line, one end of the second microstrip line and one end of the fifth microstrip line, the other end of the first microstrip line is connected to the input end and one end of the first open-circuit stub, the other end of the second microstrip line is connected to the output end and one end of the third microstrip line, the other end of the third microstrip line is connected to one end of the second open-circuit stub, the other end of the fifth microstrip line is connected to one end of the fifth open-circuit stub, and the other end of the fourth microstrip line is connected to one end of the third open-circuit stub and one end of the fourth open-circuit stub.

[0006] Optionally, the first microstrip line and the second microstrip line, and the third open-circuit stub and the fourth open-circuit stub are symmetrically arranged about the fourth microstrip line.

[0007] Optionally, the first open-circuit stub, the first microstrip line, the second microstrip line, the third microstrip line, the third open-circuit stub, the fourth open-circuit stub and the fifth open-circuit stub are arranged in parallel and are all perpendicular to the fourth microstrip line, the fifth microstrip line and the second open-circuit stub.

[0008] Optionally, the characteristic impedance of the first microstrip line, the characteristic impedance of the second microstrip line, the characteristic impedance of the third microstrip line, the characteristic impedance of the fifth microstrip line, the characteristic impedance of the first open-circuit stub, the characteristic impedance of the second open-circuit stub and the characteristic impedance of the fifth open-circuit stub are the same; the characteristic impedance of the third open-circuit stub and the characteristic impedance of the fourth open-circuit stub are the same and twice the characteristic impedance of the fourth microstrip line.

[0009] Optionally, the electrical length of the first microstrip line, the electrical length of the second microstrip line, the electrical length of the fourth microstrip line, the electrical length of the third open-circuit stub and the electrical length of the fourth open-circuit stub are all a quarter of the wavelength corresponding to the center frequency of the stopband, the sum of the electrical length of the fifth microstrip line and the electrical length of the fifth open-circuit stub is a quarter of the wavelength corresponding to the center frequency of the stopband, and the electrical length of the first open-circuit stub is equal to the electrical length of the third microstrip line.

[0010] Optionally, the electrical length of the first open-circuit stub is calculated by the formula where λ is the wavelength corresponding to the center frequency of the stopband, Z1 is the characteristic impedance of the first microstrip line, and Z2 is the characteristic impedance of the fourth microstrip line; and the electrical length of the second open-circuit stub is calculated by the formula where λ is the wavelength corresponding to the center frequency of the stopband, Z1 is the characteristic impedance of the first microstrip line, and Z2 is the characteristic impedance of the fourth microstrip line.

[0011] To solve the above technical problems, another technical solution adopted by the present application is to provide a low-pass filter comprising the above topology.

[0012] To solve the above technical problems, another technical solution adopted by the present application is to provide a communication device comprising the above low-pass filter.

[0013] The beneficial effect of the embodiment of the present application is: different from the prior art, the embodiment of the present application provides a topology structure, including an input end, an output end, a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a fifth microstrip line, a first open-circuit stub, a second open-circuit stub, a third open-circuit stub, a fourth open-circuit stub and a fifth open-circuit stub. One end of the fourth microstrip line is connected with one end of the first microstrip line, one end of the second microstrip line and one end of the fifth microstrip line, the other end of the first microstrip line is connected with the input end and one end of the first open-circuit stub, the other end of the second microstrip line is connected with the output end and one end of the third microstrip line, the other end of the third microstrip line is connected with one end of the second open-circuit stub, the other end of the fifth microstrip line is connected with one end of the fifth open-circuit stub, and the other end of the fourth microstrip line is connected with one end of the third open-circuit stub and one end of the fourth open-circuit stub. The topology structure is simple and can be used for low-pass filter design; two transmission poles f op1 、 ep1 in the passband of the low-pass filter based on the topology structure ensure the flatness in the passband, five transmission zeros f z1 、 z2 、 z3 、 z4 、 z5 ensure the high selectivity, high isolation and wide stopband of the low-pass filter. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by the drawings without creative labor for those skilled in the art.

[0015] Figure 1 is a topology structure of a low-pass filter provided by the embodiment of the present application;

[0016] Figure 2 is a layout of a low-pass filter example provided by the embodiment of the present application;

[0017] Figure 3 is an S parameter simulation result graph of a low-pass filter example provided by the embodiment of the present application;

[0018] Figure 4 is an analysis process schematic diagram of designing a low-pass filter based on a topology structure provided by the embodiment of the present application;

[0019] Figure 5 is a topology structure schematic diagram of an odd mode form provided by the embodiment of the present application;

[0020] Figure 6is a topological structure diagram in an even mode form provided by an embodiment of the present application. DETAILED DESCRIPTION

[0021] For the purpose of understanding the present application, the present application will be described in further detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or one or more intervening elements can be present therebetween. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or one or more intervening elements can be present therebetween. The terms "vertical", "horizontal", "left", "right", and similar expressions used in the present specification are for the purpose of illustration only.

[0022] Unless otherwise defined, all technical and scientific terms used in the present specification are the same as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the present specification are only for the purpose of describing specific embodiments of the present application and are not intended to limit the present application. The term "and / or" used in the present specification includes any and all combinations of one or more of the associated listed items.

[0023] The present application provides a topological structure 100, please refer to Figure 1 The topological structure 100 includes an input port 10, a first microstrip line 20, a second microstrip line 21, a third microstrip line 22, a fourth microstrip line 23, a fifth microstrip line 24, a first open stub 30, a second open stub 31, a third open stub 32, a fourth open stub 33, a fifth open stub 34, and an output port 40. One end of the fourth microstrip line 23 is connected to one end of the first microstrip line 20, one end of the second microstrip line 21, and one end of the fifth microstrip line 24. The other end of the first microstrip line 20 is connected to the input port 10 and one end of the first open stub 30. The other end of the second microstrip line 21 is connected to the output port 40 and one end of the third microstrip line 22. The other end of the third microstrip line 22 is connected to one end of the second open stub 31. The other end of the fifth microstrip line 24 is connected to one end of the fifth open stub 34. The other end of the fourth microstrip line 23 is connected to one end of the third open stub 32 and one end of the fourth open stub 33.

[0024] In some embodiments, the first microstrip line 20 and the second microstrip line 21, the third open stub 32, and the fourth open stub 33 are symmetrically arranged about the fourth microstrip line 23. The first open stub 30, the first microstrip line 20, the second microstrip line 21, the third microstrip line 22, the third open stub 32, the fourth open stub 33, and the fifth open stub 34 are arranged in parallel and are all perpendicular to the fourth microstrip line 23, the fifth microstrip line 24, and the second open stub 31.

[0025] In some embodiments, the characteristic impedance of the first microstrip line 20, the characteristic impedance of the second microstrip line 21, the characteristic impedance of the third microstrip line 22, the characteristic impedance of the fifth microstrip line 24, the characteristic impedance of the first open stub 30, the characteristic impedance of the second open stub 31 and the characteristic impedance of the fifth open stub 34 are the same; the characteristic impedance of the third open stub 32 and the characteristic impedance of the fourth open stub 33 are the same and are twice the characteristic impedance of the fourth microstrip line 23. The electrical length of the first microstrip line 20, the electrical length of the second microstrip line 21, the electrical length of the fourth microstrip line 23, the electrical length of the third open stub 32 and the electrical length of the fourth open stub 33 are all a quarter of the corresponding wavelength at the center frequency of the stopband, the sum of the electrical length of the fifth microstrip line 24 and the electrical length of the fifth open stub 34 is a quarter of the corresponding wavelength at the center frequency of the stopband, and the electrical length of the first open stub 30 is equal to the electrical length of the third microstrip line 22.

[0026] The electrical length of the first open stub 30 is calculated by the formula

[0027] wherein λ is the wavelength corresponding to the center frequency of the stopband, Z1 is the characteristic impedance of the first microstrip line 20, and Z2 is the characteristic impedance of the fourth microstrip line 23.

[0028] The electrical length of the second open stub 31 is calculated by the formula

[0029] wherein λ is the wavelength corresponding to the center frequency of the stopband, Z1 is the characteristic impedance of the first microstrip line 20, and Z2 is the characteristic impedance of the fourth microstrip line 23.

[0030] In order to facilitate the reader to understand the inventive concept of the present application, the following simulation experiments are carried out on the topology structure 100, please refer to Figure 2 The topology structure 100 is arranged on a circuit board (not shown in the figure), the size of the circuit board (not shown in the figure) is 26.0mm*13.0mm, the thickness is 0.813mm, the dielectric constant is 3.38, and the dielectric loss is 0.0022. One set of optimized parameters is: l 1H =8.5mm, l 1V =3.5mm, l2=9.75mm, l 3H =9.6mm, l 3V =1.15mm, l4=9.75mm, l5=9.75mm, w1=w2=w3=0.1mm, w4=2w5=3.3mm. Please refer to Figure 3 The S-parameter simulation result is that the passband range with a reflection coefficient less than -10dB is 0.935GHz, the maximum insertion loss in the passband is 0.482dB, and it has the characteristic of low insertion loss. In the passband, there are two transmission poles, respectively f op1 =0GHz and fep1 = 0.657 GHz, and the two transmission poles ensure the flatness in the passband. The stopband with isolation greater than 20 dB ranges from 1.939 to 9.943 GHz, and there are five transmission zeros in the stopband, which are f z1 = 2.441 GHz, f z4 = 3.945 GHz, f z2 = 4.782 GHz, f z5 = 5.566 GHz, f z3 = 7.767 GHz, and the five transmission zeros ensure the high isolation in the stopband. The attenuation rate of the passband edge is 53 dB / GHz, which shows high selectivity; and the ratio of the maximum frequency of the stopband to the maximum frequency of the passband is 8.3, which shows wide stopband characteristics.

[0031] In the embodiment of the present application, the topology structure 100 includes an input end 10, a first microstrip line 20, a second microstrip line 21, a third microstrip line 22, a fourth microstrip line 23, a fifth microstrip line 24, a first open-circuit stub 30, a second open-circuit stub 31, a third open-circuit stub 32, a fourth open-circuit stub 33, a fifth open-circuit stub 34, and an output end 40. One end of the fourth microstrip line 23 is connected to one end of the first microstrip line 20, one end of the second microstrip line 21, and one end of the fifth microstrip line 24, the other end of the first microstrip line 20 is connected to the input end 10 and one end of the first open-circuit stub 30, the other end of the second microstrip line 21 is connected to the output end 40 and one end of the third microstrip line 22, the other end of the third microstrip line 22 is connected to one end of the second open-circuit stub 31, the other end of the fifth microstrip line 24 is connected to one end of the fifth open-circuit stub 34; the other end of the fourth microstrip line 23 is connected to one end of the third open-circuit stub 32 and one end of the fourth open-circuit stub 33. The topology structure 100 has a simple structure and can be used for low-pass filter design. The low-pass filter based on the topology structure 100 has two transmission poles f op1 , f ep1 in the passband, which ensures the flatness in the passband, and five transmission zeros f z1 , f z2 , f z3 , f z4 , f z5 in the stopband, which ensures the high selectivity, high isolation, and wide stopband of the low-pass filter.

[0032] The present application also provides a low-pass filter embodiment, which includes the above-mentioned topology structure 100, and the structure and functions of the topology structure 100 can be referred to the above-mentioned embodiments, which will not be repeated here.

[0033] For the convenience of readers to understand, the following provides the idea of designing a low-pass filter with higher performance based on the above topology 100, wherein based on the above topology 100, in order to obtain a low-pass filter with higher performance, the largest possible Z1 value and the smallest possible Z2 value can be used, the Z1 value is related to the dielectric constant, height, etching precision and other parameters of the circuit board, and the Z2 value is related to the dielectric constant, height and stopband center frequency and other parameters of the circuit board.

[0034] Please refer to Figure 4 The analysis process of designing a low-pass filter based on the above topology 100 includes:

[0035] Step 101: equivalent the topology 100 to a symmetric structure, and obtain the transmission poles of the topology 100 by using the odd-even mode analysis method;

[0036] Step 102: calculate the transmission zero of the topology 100;

[0037] Step 103: introduce two transmission zeros, and analyze to obtain the electrical length of the first open stub and the second open stub.

[0038] Wherein, step 101 is specifically: when θ 1H = λ / 4 and θ 1V = 0, the topology 100 can be equivalent to a symmetric structure, and the transmission poles thereof can be analyzed by using the odd-even mode;

[0039] Please refer to Figure 5 The odd mode form of the symmetric topology structure is that one end of the first microstrip line 20 and one end of the first open stub 30 are connected with the input end, the other end of the first microstrip line 20 is grounded, the first microstrip line 20 and the first open stub 30 are arranged in parallel, and the characteristic impedances of the first microstrip line 20 and the first open stub 30 are both Z1, and the electrical lengths thereof are both the quarter wavelength corresponding to the stopband center frequency. When the input admittance Y ino is infinite, it can be obtained that the topology 100 has two odd mode transmission poles, which are f op1 = 0 and f op2 = f0, wherein f0 is the center frequency of the wide stopband;

[0040] Please refer to Figure 6The even mode form of the symmetric topology structure includes the first microstrip line 20, the fourth microstrip line 23, the fifth microstrip line 24, the first open stub 30, the third open stub 32 and the fifth open stub 34. One end of the first microstrip line 20 is connected with one end of the fourth microstrip line 23 and one end of the fifth microstrip line, the other end of the first microstrip line is connected with the first open stub 30 and the input end 10, the other end of the fourth microstrip line 23 is connected with one end of the third open stub 32, and the other end of the fifth microstrip line 24 is connected with one end of the fifth open stub 34. The characteristic impedance of the first microstrip line 20 and the characteristic impedance of the first open stub are both Z1, the characteristic impedance of the fifth microstrip line 24 and the characteristic impedance of the fifth open stub 34 are both 2Z1, and the characteristic impedance of the fourth microstrip line 23 and the characteristic impedance of the third open stub 32 are both 2Z2; the electrical length of the first microstrip line 20, the electrical length of the fourth microstrip line 23, the electrical length of the first open stub 30, and the electrical length of the third open stub 32 are all one quarter of the wavelength corresponding to the center frequency of the stopband, and the sum of the electrical length of the fifth microstrip line 24 and the electrical length of the fifth open stub 34 is one quarter of the wavelength corresponding to the center frequency of the stopband. When the input admittance Y ine is infinite, it can be obtained that the topology structure 100 has three even mode transmission poles, respectively

[0041]

[0042]

[0043]

[0044] Step 102 is specifically: multiplying the ABCD matrices of the cascade resonators constituting the topology structure 100 in turn to obtain the ABCD matrix corresponding to the topology structure 100, and converting the ABCD matrix of the topology structure 100 into the corresponding S matrix. When |S 21 | = 0, it can be obtained that the topology structure 100 has three transmission zeros, respectively f z2 = f0,

[0045] Step 103 is specifically: the relative positions of the two odd mode transmission poles, the three even mode transmission poles and the three transmission zeros are f op1 < f ep1 < f z1 < f ep2 < f oep2 = f z2 < f ep3 < f z3 , and the relative positions are not affected by the values of the parameters Z1 and Z2. In order to ensure that the filter designed based on this topology structure is a low-pass filter, two transmission zeros f z4 and fz5 and f z4 = f ep2 , f z5 = f ep3 This is determined by the characteristics of the filter: when the transmission pole and the transmission zero coincide, the performance of the final filter will only show the transmission zero. Therefore, the two additional transmission zeros will make the low-pass filter have two transmission poles in the passband to ensure the flatness in the passband, and five transmission zeros in the stopband to ensure the high selectivity, high isolation and wide stopband of the low-pass filter. The transmission zero f z5 is introduced by the first open-circuit stub, therefore, the length of the first open-circuit stub 30 must be:

[0046]

[0047] The transmission zero f z4 is introduced by the third microstrip line 22 and the second open-circuit stub 31, therefore, the sum of the electrical lengths of the third microstrip line 22 and the second open-circuit stub 31 must be

[0048]

[0049] The application also provides a communication device, which comprises the low-pass filter described above, and the structure and function of the low-pass filter can be referred to the above embodiments, which will not be repeated here.

[0050] It should be noted that the specification and drawings of the present application give the preferred embodiments of the present application, but the present application can be realized in many different forms, and is not limited to the embodiments described in the specification, and these embodiments are not additional limitations on the content of the present application, and the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive. Furthermore, the above technical features continue to combine, forming various embodiments not listed above, which are considered to be within the scope of the present application; further, for those skilled in the art, the above description can be improved or changed, and all these improvements and changes should be within the protection scope of the appended claims of the present application.

Claims

1. A topology, characterized in that, The input end, the output end, the first microstrip line, the second microstrip line, the third microstrip line, the fourth microstrip line, the fifth microstrip line, the first open-circuit stub, the second open-circuit stub, the third open-circuit stub, the fourth open-circuit stub and the fifth open-circuit stub are included. One end of the fourth microstrip line is connected with one end of the first microstrip line, one end of the second microstrip line and one end of the fifth microstrip line, the other end of the first microstrip line is connected with the input end and one end of the first open-circuit stub, the other end of the second microstrip line is connected with the output end and one end of the third microstrip line, the other end of the third microstrip line is connected with one end of the second open-circuit stub, the other end of the fifth microstrip line is connected with one end of the fifth open-circuit stub, and the other end of the fourth microstrip line is connected with one end of the third open-circuit stub and one end of the fourth open-circuit stub. The first microstrip line and the second microstrip line, and the third open-circuit stub and the fourth open-circuit stub are symmetrically arranged about the fourth microstrip line. The first open-circuit stub, the first microstrip line, the second microstrip line, the third microstrip line, the third open-circuit stub, the fourth open-circuit stub, the fifth open-circuit stub are arranged in parallel and are perpendicular to the fourth microstrip line, the fifth microstrip line and the second open-circuit stub.

2. The topology of claim 1, wherein , The characteristic impedance of the first microstrip line, the characteristic impedance of the second microstrip line, the characteristic impedance of the third microstrip line, the characteristic impedance of the fifth microstrip line, the characteristic impedance of the first open-circuit stub, the characteristic impedance of the second open-circuit stub and the characteristic impedance of the fifth open-circuit stub are the same. The characteristic impedance of the third open-circuit stub and the characteristic impedance of the fourth open-circuit stub are the same and are twice the characteristic impedance of the fourth microstrip line.

3. The topology of claim 1, wherein , The electrical length of the first microstrip line, the electrical length of the second microstrip line, the electrical length of the fourth microstrip line, the electrical length of the third open-circuit stub and the electrical length of the fourth open-circuit stub are all one quarter of the corresponding wavelength at the center frequency of the stop band, the sum of the electrical length of the fifth microstrip line and the electrical length of the fifth open-circuit stub is one quarter of the corresponding wavelength at the center frequency of the stop band, and the electrical length of the first open-circuit stub is equal to the electrical length of the third microstrip line.

4. The topology structure of claim 1, wherein The electrical length of the first open-circuit stub is calculated by the formula wherein The electrical length of the second open-circuit stub is calculated by the formula is the wavelength corresponding to the center frequency of the stop band, Z1is the characteristic impedance of the first microstrip line, and Z2is the characteristic impedance of the fourth microstrip line. The topology structure of any one of claims 1-4 is included. wherein The low-pass filter of claim 5 is included. is the wavelength corresponding to the center frequency of the stop band, Z1is the characteristic impedance of the first microstrip line, and Z2is the characteristic impedance of the fourth microstrip line.

5. A low pass filter characterized by, ​ 6. A communication device, characterized by ​

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