A topology of a dual-band filter with a small center frequency ratio and a filter

Abstract

The application discloses a kind of topology structure of small center frequency ratio of double-passband filter and filter, and the topology structure includes microstrip line, one end of the microstrip line is symmetrically connected with the one end of first parallel five lines and the one end of second parallel five lines, the other end of the microstrip line is symmetrically connected with the one end of first short-circuit stub and the one end of second short-circuit stub;The other end of the first parallel five lines is connected with input end, the other end of the second parallel five lines is connected with output end, the other end of the first short-circuit stub and the other end of the second short-circuit stub are grounded respectively.The application solves the problem that the center frequency ratio of two channels of existing double-passband filter is large.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of filter, in particular to a topology structure of a dual-passband filter with a small center frequency ratio and the filter. BACKGROUND

[0002] With the rapid development of modern wireless communication technology, the radio frequency receiving front end needs to be compatible with different communication systems and provide more abundant services to meet the growing demand of people's digital application. In this context, the microstrip dual-passband filter with low cost, small size, low profile, light weight and easy integration attracts the attention of scholars and engineers and has been deeply studied. However, the microstrip dual-passband filters reported at present mostly have the problems of narrow bandwidth, large insertion loss, poor isolation, large size and large center frequency ratio of two channels, which seriously affect their use in modern wireless communication systems. SUMMARY

[0003] The main purpose of the present application is to provide a topology structure of a dual-passband filter with a small center frequency ratio and the filter, which aims to solve the problem of large center frequency ratio of two channels of the existing dual-passband filter.

[0004] To achieve the above purpose, the present application provides a topology structure of a dual-passband filter with a small center frequency ratio, which comprises a microstrip line, one end of the microstrip line is symmetrically connected with one end of a first parallel five-line and one end of a second parallel five-line, the other end of the microstrip line is symmetrically connected with one end of a first short-circuit stub and one end of a second short-circuit stub; the other end of the first parallel five-line is connected with an input end, the other end of the second parallel five-line is connected with an output end, and the other end of the first short-circuit stub and the other end of the second short-circuit stub are grounded respectively.

[0005] Optionally, the electrical length of the microstrip line, the electrical length of the first parallel five-line, the electrical length of the second parallel five-line, the electrical length of the first short-circuit stub and the electrical length of the second short-circuit stub are all equal.

[0006] Optionally, the electrical length of the microstrip line, the electrical length of the first parallel five-line, the electrical length of the second parallel five-line, the electrical length of the first short-circuit stub and the electrical length of the second short-circuit stub are all set to the corresponding quarter wavelength at the center frequency of the middle stopband of the two passbands.

[0007] Optionally, the first parallel five-line and the second parallel five-line each comprise five transmission lines arranged in parallel with each other.

[0008] Optionally, the parameters of the topology structure include the width of the transmission line, the spacing between adjacent transmission lines, the width of the microstrip line and the width of the first short-circuit stub and the second short-circuit stub.

[0009] In order to achieve the above object, the application further provides a filter comprising the filter with the topological structure as described above.

[0010] Optionally, the filter further comprises a circuit board, and the circuit board has a dielectric constant of 3.38, a dielectric loss of 0.0022 and a thickness of 0.813 mm.

[0011] Optionally, the filter has a circuit board with a size of 25.4 mm*12.0 mm.

[0012] Optionally, the first parallel five-line and the second parallel five-line have a length of 9.7 mm, the microstrip line has a length of 10.2 mm, the first short-circuit stub and the second short-circuit stub have a length of 10.35 mm, the first parallel five-line and the second parallel five-line have a transmission line width of 0.1 mm, the first parallel five-line and the second parallel five-line have a transmission line spacing of 0.06 mm, the microstrip line has a width of 2.2 mm, and the first short-circuit stub and the second short-circuit stub have a width of 2.0 mm.

[0013] The application has the advantages that the topological structure of the filter is improved, the filter comprises a microstrip line, one end of the microstrip line is symmetrically connected with one end of a first parallel five-line and one end of a second parallel five-line, the other end of the microstrip line is symmetrically connected with one end of a first short-circuit stub and one end of a second short-circuit stub, the other end of the first parallel five-line is connected with an input end, the other end of the second parallel five-line is connected with an output end, and the other end of the first short-circuit stub and the other end of the second short-circuit stub are respectively grounded, and the filter with the topological structure has the advantages of wide bandwidth, small insertion loss, high isolation, small size and small ratio of passband center frequency. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only show some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from the drawings shown without any creative effort.

[0015] Figure 1 The topological structure of the filter of the application;

[0016] Figure 2 The layout of the filter based on the topological structure of the application;

[0017] Figure 3 The simulation S parameter of the filter of the application changes with different s P ;

[0018] Figure 4 Fig. 1 is a diagram showing the change of the S parameter of the filter of the present application with different w1; P

[0019] Figure 5 Fig. 2 is a diagram showing the change of the S parameter of the filter of the present application with different w2;

[0020] Figure 6 Fig. 3 is a diagram showing the change of the S parameter of the filter of the present application with different w1;

[0021] Figure 7 Fig. 4 is a diagram showing the simulation result of the S parameter of the filter of the present application;

[0022] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0024] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement condition, etc. between the components in a certain posture (as shown in the drawings), and if the certain posture changes, the directional indications also change accordingly.

[0025] In addition, if the embodiments of the present application involve descriptions of "first", "second", etc., the descriptions of "first", "second", etc. are only for description purposes, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first" and "second" can explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing throughout the text is that it includes three parallel schemes, for example, "A and / or B" includes A scheme, or B scheme, or A and B schemes. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that a person skilled in the art can realize it, and when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist and is not within the scope of protection claimed by the present application.

[0026] An embodiment of the present application proposes a topology structure of a double-passband filter with a small center frequency ratio, which is referred to as Figure 1 ​, including a microstrip line, one end of the microstrip line is symmetrically connected with one end of a first parallel five-line and one end of a second parallel five-line, the other end of the microstrip line is symmetrically connected with one end of a first short-circuit stub and one end of a second short-circuit stub; the other end of the first parallel five-line is connected with an input end, the other end of the second parallel five-line is connected with an output end, and the other end of the first short-circuit stub and the other end of the second short-circuit stub are respectively grounded. As shown in Figure 1 , in this embodiment, the topology structure adopts a symmetric structure, the first parallel five-line and the second parallel five-line are the same, and the first parallel five-line and the second parallel five-line are symmetrically arranged based on the microstrip line, the first short-circuit stub and the second short-circuit stub are the same, and the first short-circuit stub and the second short-circuit stub are symmetrically arranged based on the microstrip line, thereby forming a topology structure of a double-passband filter.

[0027] Further, the electrical length of the microstrip line, the electrical length of the first parallel five-line, the electrical length of the second parallel five-line, the electrical length of the first short-circuit stub and the electrical length of the second short-circuit stub are equal. Specifically, the electrical length of the microstrip line, the electrical length of the first parallel five-line, the electrical length of the second parallel five-line, the electrical length of the first short-circuit stub and the electrical length of the second short-circuit stub are respectively set to a corresponding quarter wavelength at a center frequency of a stopband between two passbands.

[0028] Further, the first parallel five-line and the second parallel five-line respectively include five transmission lines arranged in parallel with each other. According to microwave common sense, synchronously changing the values of the physical length of the parallel five-line, the physical length of the microstrip line and the physical length of the short-circuit stub in equal amounts can inversely linearly adjust the working frequency range of the two passbands. In this embodiment, in order to ensure that the filter designed based on the topology structure has the advantages of wide bandwidth, small insertion loss, high isolation, small size and small passband center frequency ratio, the design parameters of the topology structure of this embodiment include the width of the transmission line, the spacing between adjacent transmission lines, the width of the microstrip line and the width of the first short-circuit stub and the second short-circuit stub. Among them, the width of the microstrip line should be slightly greater than or equal to the width of the first short-circuit stub and the second short-circuit stub. The characteristics of the filter designed based on the topology structure of this embodiment will be described in detail in the filter of another embodiment.

[0029] Another embodiment of the present application also provides a filter, which includes the filter with the topology structure designed according to any one of the above-mentioned embodiments. The filter further includes a circuit board, the dielectric constant of the circuit board is 3.38, the dielectric loss is 0.0022, and the thickness is 0.813 mm. The circuit board of the filter is 25.4 mm*12.0 mm.

[0030] Further, referring to Figure 2 , the length of the first parallel five-line and the second parallel five-line is set to l P= 0.1 mm, the transmission line spacing of the first and second parallel five-line is set as s P = 0.1 mm, the transmission line spacing of the first and second parallel five-line is set as s P = 0.06 mm, the width of the microstrip line is set as w1 = 2.2 mm, and the width of the first and second short-circuit stubs is set as w2 = 2.0 mm.

[0031] It should be noted that in the previous embodiment, the design parameters of the topology structure affecting the filter performance include the width of the transmission line, the spacing between adjacent transmission lines, the width of the microstrip line, and the width of the first and second short-circuit stubs. Therefore, in the present embodiment, the influence of each parameter on the filter performance will be described in detail.

[0032] Referring to Figure 3 , changing the value of the spacing s P between adjacent transmission lines constituting the parallel five-line does not change the bandwidth of the dual-passband filter and the ratio of the two passband center frequencies, but by adjusting the value of the spacing s P between adjacent transmission lines constituting the parallel five-line, the reflection coefficient and the insertion loss flatness in the passband can be optimized.

[0033] Referring to Figure 4 , the influence of the spacing s p between adjacent transmission lines constituting the parallel five-line on the performance of the dual-passband filter is similar, changing the value of the width w P of the transmission line constituting the parallel five-line does not change the bandwidth of the dual-passband filter and the ratio of the two passband center frequencies, but by adjusting the value of the width w P of the transmission line constituting the parallel five-line, the reflection coefficient and the insertion loss flatness in the passband can be optimized.

[0034] Referring to Figure 5 , changing the value of the width w1 of the microstrip line does not change the position of the lower passband edge of the first passband, but changes the positions of the upper passband edge of the first passband, the lower passband edge of the second passband, and the upper passband edge of the second passband. In other words, changing the value of the width w1 of the microstrip line not only changes the bandwidth of the two passbands, but also changes the ratio of the two passband center frequencies. As the value of the width w1 of the microstrip line increases, the bandwidth of the two passbands decreases, but the ratio of the two passband center frequencies increases. In addition, by changing the value of the width w1 of the microstrip line, the reflection coefficient and the insertion loss flatness in the passband can also be optimized.

[0035] Referring to Figure 6Changing the stub width w2 does not alter the positions of the lower passband edge, upper passband edge, or upper passband edge of the first passband, but it does change the position of the upper passband edge of the second passband. In other words, changing the stub width w2 only changes the bandwidth of the second passband and the ratio of the center frequencies of the two passbands; it does not affect the bandwidth of the first passband. As the stub width w2 increases, the bandwidth of the second passband increases, but the ratio of the center frequencies of the two passbands decreases. Furthermore, changing the stub width w2 can also optimize the reflection coefficient and the flatness of the insertion loss within the passband.

[0036] The above analysis shows that the ratio of the passband bandwidth to the center frequency of the wide dual-passband filter designed based on the topology of this invention is controlled by parameters w1 and w2, and the adjustment parameter s P and w P The passband reflection coefficient and insertion loss flatness can be optimized independently without affecting the ratio of passband bandwidth to center frequency. However, regardless of how the parameter s is changed... P w P Based on this topology, the filters designed can only be dual-passband filters.

[0037] refer to Figure 7 Based on the design parameters of the filter topology used in this embodiment, and corresponding simulation results, in this embodiment, the lengths of the first and second parallel quincunx lines are set to l. P = 9.7mm, the length of the microstrip line is set to l1 = 10.2mm, the length of the first short-circuit stub and the second short-circuit stub is set to l2 = 10.35mm; the transmission line width of the first parallel five-wire and the second parallel five-wire is set to w P =0.1mm, the transmission line spacing of the first and second parallel pentagons is set to s P =0.06mm, the width of the microstrip line is set to w1 = 2.2mm, and the width of the first short-circuit stub and the second short-circuit stub is set to w2 = 2.0mm.

[0038] Depend on Figure 7It can be seen that in the first passband, the impedance bandwidth range with the reflection coefficient less than -10dB is 1.546 to 3.728GHz, the passband center frequency is 2.637GHz, the passband absolute bandwidth is 2.182GHz, and the passband relative bandwidth is 82.7%; in the second passband, the impedance bandwidth range with the reflection coefficient less than -10dB is 5.994 to 8.664GHz, the passband center frequency is 7.329GHz, the passband absolute bandwidth is 2.67GHz, and the passband relative bandwidth is 36.4%. In addition, there are two transmission poles in the first passband, which are respectively located at 1.661, 2.723, 3.348GHz; there are also three transmission poles in the second passband, which are respectively located at 6.578, 7.102, 8.518GHz, and the six transmission poles can ensure the flatness in the passband.

[0039] In the stopband between the two passbands, the stopband bandwidth range with the isolation greater than 15dB is 4.538 to 5.262GHz, the stopband center frequency is 4.9GHz, the stopband absolute bandwidth is 0.724GHz, and the stopband relative bandwidth is 14.8%. There are also six transmission zeros in the stopband, which are respectively located at 0, 4.744, 5.203, 10.378, 10.501, 10.785GHz. The six transmission zeros not only ensure the high selectivity of the wide dual-passband filter, but also ensure the high isolation of the stopband.

[0040] It can be seen from the comprehensive simulation results that for the dual-passband filter with the first passband relative bandwidth of 82.7% and the second passband relative bandwidth of 36.4%, the ratio of the center frequencies of the two passbands is only 2.78, which has the characteristic of small ratio of passband center frequencies.

[0041] The above only describes optional embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structural transformation made according to the content of the present application specification and drawings, or direct / indirect application in other related technical fields is included in the patent protection scope of the present application.

Claims

1. A topology for a dual-band filter with a small center frequency ratio, characterized by, The microstrip line is symmetrically connected with one end of a first parallel five-line and one end of a second parallel five-line at one end, and is symmetrically connected with one end of a first short-circuit stub and one end of a second short-circuit stub at the other end; the other end of the first parallel five-line is connected with an input end, the other end of the second parallel five-line is connected with an output end, and the other end of the first short-circuit stub and the other end of the second short-circuit stub are respectively grounded. The electrical length of the microstrip line, the electrical length of the first parallel five-line, the electrical length of the second parallel five-line, the electrical length of the first short-circuit stub and the electrical length of the second short-circuit stub are all equal. The first parallel five-line and the second parallel five-line respectively include five transmission lines arranged in parallel.

2. The topology of a double pass-band filter with small center frequency ratio according to claim 1, characterized in that, The electrical length of the microstrip line, the electrical length of the first parallel five-line, the electrical length of the second parallel five-line, the electrical length of the first short-circuit stub and the electrical length of the second short-circuit stub are all set to be a quarter of the wavelength corresponding to the center frequency of a stop band between two pass bands.

3. The topology of a double pass-band filter with small center frequency ratio according to claim 1, characterized in that, The parameters of the topological structure include the width of the transmission line, the spacing between adjacent transmission lines, the width of the microstrip line and the width of the first short-circuit stub and the second short-circuit stub.

4. A filter, characterized by, The filter includes the topological structure design of any one of claims 1-3.

5. The filter of claim 4, wherein, The filter further includes a circuit board, and the circuit board has a dielectric constant of 3.38, a dielectric loss of 0.0022 and a thickness of 0.813 mm.

6. The filter of claim 5, wherein, The size of the circuit board of the filter is 25.4 mm*12.0 mm.

7. The filter of claim 4, wherein, The length of the first parallel five-line and the second parallel five-line is set to be 9.7 mm, the length of the microstrip line is set to be 10.2 mm, and the length of the first short-circuit stub and the second short-circuit stub is set to be 10.35 mm; the width of the transmission line of the first parallel five-line and the second parallel five-line is set to be 0.1 mm, the spacing of the transmission line of the first parallel five-line and the second parallel five-line is set to be 0.06 mm, the width of the microstrip line is set to be 2.2 mm, and the width of the first short-circuit stub and the second short-circuit stub is set to be 2.0 mm.

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