Microstrip topological structure and dual-passband filter

Abstract

The utility model discloses a microstrip topological structure, which comprises a first transmission line, a second transmission line, a first microstrip line, a second microstrip line, a first open-circuit branch knot, a second open-circuit branch knot, an input end and an output end, and is characterized in that the first transmission line and the second transmission line are arranged in parallel to form a parallel line; the first end of the first transmission line is sequentially connected with the first microstrip line and the input end, the second end of the first transmission line is connected with the first open-circuit branch knot, the first end of the second transmission line is connected with the second open-circuit branch knot, and the second end of the second transmission line is sequentially connected with the second microstrip line and the output end. The utility model also discloses a dual-passband filter based on the microstrip topological structure, and the dual-passband filter has the advantage of wide passband.

Description

Technical Field

[0001] The utility model relates to the technical field of filters, in particular to a microstrip topology and a dual-band filter. Background Art

[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 richer services to meet the growing digital application requirements of people. Under this background, the microstrip dual-band filter with low cost, light weight, low profile and easy integration has attracted the attention of many scholars and engineers, and in-depth research has been carried out. However, most of the reported microstrip dual-band filters currently have the defect of narrow passband, which seriously affects their use in modern high-speed information transmission communication systems. Summary of the Utility Model

[0003] In view of the above deficiencies of the prior art, the main object of the present utility model is to provide a microstrip topology and a dual-band filter, aiming to solve the problem of narrow passband of the existing microstrip dual-band filter.

[0004] To solve the above technical problems, the technical solution adopted by the present utility model is as follows:

[0005] A microstrip topology includes a first transmission line, a second transmission line, a first microstrip line, a second microstrip line, a first open stub, a second open stub, an input end and an output end. The first transmission line and the second transmission line are arranged in parallel to form a parallel line. The first end of the first transmission line is sequentially connected to the first microstrip line and the input end, the second end of the first transmission line is connected to the first open stub, the first end of the second transmission line is connected to the second open stub, and the second end of the second transmission line is sequentially connected to the second microstrip line and the output end.

[0006] Optionally, the first microstrip line, the second microstrip line, the first open stub and the second open stub are all perpendicular to the first transmission line and the second transmission line.

[0007] Optionally, the first microstrip line, the first open stub, the second microstrip line and the second open stub all extend away from the parallel line.

[0008] Optionally, the first ends of the first transmission line and the second transmission line are on the same side, and the second ends of the first transmission line and the second transmission line are on the same side.

[0009] Optionally, the electrical length of the parallel lines is 0.25λ; the electrical lengths of the first transmission line and the second transmission line are equal, and the electrical lengths of the first open stub and the second open stub are equal; the sum of the electrical length of the first transmission line and the electrical length of the first open stub is 0.25λ, where λ is the wavelength corresponding to the center frequency of the stopband between the two passbands of the microstrip topology-based dual-band filter.

[0010] Optionally, the electrical length of the first open stub is greater than the electrical length of the first microstrip line.

[0011] Optionally, the characteristic impedances of the first microstrip line, the second microstrip line, the first open stub, and the second open stub are equal.

[0012] Another technical solution adopted by the present invention is:

[0013] A dual-band filter includes the above microstrip topology.

[0014] Optionally, it further includes a circuit board. The microstrip topology is disposed on the circuit board. The circuit board has a dielectric constant of 3.38, a dielectric loss of 0.0022, a thickness of 0.813 mm, and a size of 7.6 mm * 11.9 mm.

[0015] Optionally, the specific parameter settings on the circuit board are:

[0016] l P = 6.4 mm, l P represents the physical lengths of the first transmission line and the second transmission line;

[0017] s P = 0.1 mm, s P represents the distance between the first transmission line and the second transmission line;

[0018] w P = 0.1 mm, w P represents the physical widths of the first transmission line and the second transmission line;

[0019] l1 = 1.4 mm, l1 represents the physical lengths of the first microstrip line and the second microstrip line;

[0020] l2 = 5.8 mm, l2 represents the physical lengths of the first open stub and the second open stub;

[0021] w1 = 0.1 mm, where w1 represents the physical width of the first microstrip line, the physical width of the second microstrip line, the physical width of the first open stub, and the physical width of the second open stub.

[0022] The beneficial effects of the present utility model are as follows: A new microstrip topology is proposed, and based on this topology, a dual-band filter can be designed, which has the advantage of wide bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The figure shows a schematic diagram of the microstrip topology according to an embodiment of the present utility model;

[0024] Figure 2 The figure shows a schematic diagram of the odd-mode form of the microstrip topology according to an embodiment of the present utility model;

[0025] Figure 3 The figure shows a schematic diagram of the even-mode form of the microstrip topology according to an embodiment of the present utility model;

[0026] Figure 4 The figure shows the layout layout of the dual-band filter according to an embodiment of the present utility model;

[0027] Figure 5 The figure shows another layout layout of the dual-band filter according to an embodiment of the present utility model;

[0028] Figure 6 The figure shows the S-parameter simulation results of the dual-band filter according to an embodiment of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] In order to more clearly understand the technical content, the achieved objectives, and the effects of the present utility model, the following provides a detailed description of the present utility model in combination with specific embodiments and with reference to the accompanying drawings. It should be noted that, without conflict, the embodiments of the present utility model and the features in the embodiments can be combined with each other. In the following description, many specific details are set forth in order to fully understand the present utility model. The described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts fall within the scope of protection of the present utility model.

[0030] Please refer to Figures 1-3 As shown in the figure, Embodiment 1 of the present utility model is as follows:

[0031] A microstrip topology mainly consists of two transmission lines, two microstrip lines, and two open stubs. Specifically, as Figure 1As shown, it includes a first transmission line, a second transmission line, a first microstrip line, a second microstrip line, a first open stub, a second open stub, an input end and an output end. The first transmission line and the second transmission line are arranged closely and in parallel, forming a parallel line. The first end of the first transmission line is sequentially connected to the first microstrip line and the input end, the second end of the first transmission line is connected to the first open stub, the first end of the second transmission line is connected to the second open stub, and the second end of the second transmission line is sequentially connected to the second microstrip line and the output end. The first end of the first transmission line and the first end of the second transmission line are on the same side, and the second end of the first transmission line and the second end of the second transmission line are on the same side.

[0032] The first microstrip line, the second microstrip line, the first open stub and the second open stub are all perpendicular to the first transmission line and the second transmission line. The first microstrip line, the first open stub, the second microstrip line and the second open stub all extend away from the parallel line.

[0033] The electrical length of the parallel line formed by the first transmission line and the second transmission line is 0.25λ; the electrical lengths of the first transmission line and the second transmission line are equal, and the electrical lengths of the first open stub and the second open stub are equal; the sum of the electrical length of the first transmission line and the electrical length of the first open stub is 0.25λ, where λ is the wavelength corresponding to the center frequency of the stopband between the two passbands of the dual-band filter based on the microstrip topology. The electrical length of the first open stub is greater than the electrical length of the first microstrip line.

[0034] The odd-mode characteristic impedance of the parallel line is Z oo and the even-mode characteristic impedance of the parallel line is Z oe ; the characteristic impedances of the first microstrip line, the second microstrip line, the first open stub and the second open stub are equal, and are all Z1.

[0035] Since the microstrip topology of this embodiment can be equivalent to a symmetric structure, its transmission poles can be obtained by odd-even mode analysis. To more simply calculate the transmission poles of this topology, first assume that the electrical length of the first open stub is much greater than the electrical length of the first microstrip line. At this time, the odd-mode form of this microstrip topology is as Figure 2 shown, where the electrical length of the odd-mode transmission line is a quarter wavelength corresponding to the center frequency of the stopband between the two passbands of the dual-band filter based on the microstrip topology, that is, 0.25λ, and the characteristic impedance of the odd-mode transmission line is Z oo .

[0036] When Y inoWhen = 0, it can be obtained that the microstrip topology has two transmission poles. When f0 is the center frequency of the stopband between the two passbands, the frequencies corresponding to the two odd-mode transmission poles are respectively:

[0037]

[0038] The even-mode form of the microstrip topology is as Figure 3 shown, where the electrical length of the even-mode transmission line is a quarter wavelength corresponding to the center frequency of the stopband between the two passbands of the dual-band filter based on the microstrip topology, that is, 0.25λ, and the characteristic impedance of the even-mode transmission line is Z oe .

[0039] When Y ine = 0, it can be obtained that the microstrip topology has two even-mode transmission poles. When f0 is the center frequency of the stopband between the two passbands, the frequencies corresponding to the two even-mode transmission poles are respectively:

[0040]

[0041] For this microstrip topology, its transmission zeros can be calculated by the following formula:

[0042]

[0043] After calculation, it can be obtained that the microstrip topology has three transmission zeros, and the frequencies corresponding to the three transmission zeros are respectively:

[0044] f z1 = 0

[0045] f z2 = f0

[0046] f z3 = 2f0

[0047] From the above analysis, it can be seen that the filter based on this microstrip topology has two odd-mode transmission poles, two even-mode transmission poles and three transmission zeros. And no matter how the parameters Z oo , Z oe and the value of Z1 are changed, the relative positions of the transmission zeros and poles, that is, f z1 < f ep1 < f op1 < f2 < f op2 < f ep2 < f z3, none of them will change. Therefore, based on this microstrip topology, a dual-band filter can be designed, with two transmission poles in each of the two passbands to ensure the flatness within the passbands, one transmission zero below the first passband edge and one above the fourth passband edge to ensure high selectivity, and one transmission zero between the second passband edge and the third passband edge to ensure high isolation.

[0048] Please refer to Figures 4-6 as shown, the second embodiment of the present invention is:

[0049] A dual-band filter 100, comprising a circuit board and the microstrip topology described in the first embodiment, and the microstrip topology is disposed on the circuit board. The dielectric constant of the circuit board is 3.38, the dielectric loss is 0.0022, the thickness is 0.813 mm, and the size is 7.6 mm * 11.9 mm. As Figure 4 and 5 are the layout layout diagrams of the dual-band filter of this embodiment. In the figure, 10 represents the input end and 50 represents the output end.

[0050] The specific parameter settings on the circuit board are:

[0051] l P = 6.4 mm, l P represents the physical length of the first transmission line 30 and the physical length of the second transmission line 31;

[0052] s P = 0.1 mm, s P represents the distance between the first transmission line 30 and the second transmission line 31;

[0053] w P = 0.1 mm, w P represents the physical width of the first transmission line 30 and the physical width of the second transmission line 31;

[0054] l1 = 1.4 mm, l1 represents the physical length of the first microstrip line 20 and the physical length of the second microstrip line 21;

[0055] l2 = 5.8 mm, l2 represents the physical length of the first open stub 40 and the physical length of the second open stub 41;

[0056] w1 = 0.1 mm, w1 represents the physical width of the first microstrip line 20, the physical width of the second microstrip line 21, the physical width of the first open stub 40, and the physical width of the second open stub 41.

[0057] The simulation results of the dual-band filter of this embodiment are as Figure 6As shown. It can be seen from the figure that in the first passband, the impedance bandwidth range with a reflection coefficient less than -10 dB is from 2.92 to 4.56 GHz, the center frequency of the passband is 3.74 GHz, the absolute bandwidth of the passband is 1.64 GHz, and the relative bandwidth of the passband is 43.9%; in its second passband, the impedance bandwidth range with a reflection coefficient less than -10 dB is from 9.71 to 11.19 GHz, the center frequency of the passband is 10.45 GHz, the absolute bandwidth of the passband is 1.48 GHz, and the relative bandwidth of the passband is 14.2%. From the bandwidth simulations of these two passbands, it can be known that the dual-band filter based on this microstrip topology is a wide dual-band filter. In the first passband, the maximum insertion loss is 0.51 dB; in the second passband, the maximum insertion loss is 0.63 dB. Thus, it can be seen that the dual-band filter based on this microstrip topology has the characteristic of low insertion loss.

[0058] In addition, there are two transmission poles in the first passband, located at 3.27 GHz and 4.11 GHz respectively; there are also two transmission poles in the second passband, located at 10.08 GHz and 10.88 GHz respectively. These four transmission poles can ensure the flatness within the passband.

[0059] There are also three transmission zeros in the stopband, located at 0, 7.23 GHz, and 14.79 GHz respectively. These three transmission zeros ensure the high isolation of the dual-band filter.

[0060] In summary, the microstrip topology proposed by the present utility model can be used to design a dual-band filter. The dual-band filter designed based on this microstrip topology has the advantages of wide passband, low insertion loss characteristic, and high isolation.

[0061] The above are only the embodiments of the present utility model, and do not limit the patent scope of the present utility model. Therefore, any modifications, equivalent changes, and decorations made to the above embodiments based on the technical essence of the present utility model without departing from the content of the technical solution of the present utility model still fall within the scope of the technical solution of the present utility model.

Claims

1. A microstrip topology, characterized in that, It includes a first transmission line, a second transmission line, a first microstrip line, a second microstrip line, a first open stub, a second open stub, an input end and an output end. The first transmission line and the second transmission line are arranged in parallel to form a parallel line. The first end of the first transmission line is sequentially connected to the first microstrip line and the input end, the second end of the first transmission line is connected to the first open stub, the first end of the second transmission line is connected to the second open stub, and the second end of the second transmission line is sequentially connected to the second microstrip line and the output end.

2. The microstrip topology according to claim 1, wherein The first microstrip line, the second microstrip line, the first open stub and the second open stub are all perpendicular to the first transmission line and the second transmission line.

3. The microstrip topology according to claim 1, wherein The first microstrip line, the first open stub, the second microstrip line and the second open stub all extend away from the parallel line.

4. The microstrip topology according to claim 1, characterized in that, The first ends of the first transmission line and the second transmission line are on the same side, and the second ends of the first transmission line and the second transmission line are on the same side.

5. The microstrip topology according to claim 1, characterized in that, The electrical length of the parallel line is 0.25λ; the electrical lengths of the first transmission line and the second transmission line are equal, and the electrical lengths of the first open stub and the second open stub are equal; the sum of the electrical length of the first transmission line and the electrical length of the first open stub is 0.25λ, where λ is the wavelength corresponding to the center frequency of the stopband between the two passbands of the dual-band filter based on the microstrip topology.

6. The microstrip topology according to claim 1, characterized in that, The electrical length of the first open stub is greater than the electrical length of the first microstrip line.

7. The microstrip topology according to claim 1, wherein The characteristic impedances of the first microstrip line, the second microstrip line, the first open stub and the second open stub are equal.

8. A dual-band filter, characterized in that, It includes the microstrip topology according to any one of claims 1-7.

9. The dual-band filter according to claim 8, characterized in that, It further includes a circuit board. The microstrip topology is disposed on the circuit board. The circuit board has a dielectric constant of 3.38, a dielectric loss of 0.0022, a thickness of 0.813 mm, and a size of 7.6 mm * 11.9 mm.

10. The diplexer filter according to claim 9, characterized in that, The specific parameter settings on the circuit board are as follows: l P = 6.4 mm, l P represents the physical length of the first transmission line and the physical length of the second transmission line; s P = 0.1 mm, s P represents the distance between the first transmission line and the second transmission line; w P = 0.1 mm, w P represents the physical width of the first transmission line and the physical width of the second transmission line; l1 = 1.4 mm, where l1 represents the physical lengths of the first microstrip line and the second microstrip line; l2 = 5.8 mm, where l2 represents the physical lengths of the first open stub and the second open stub; w1 = 0.1 mm, where w1 represents the physical widths of the first microstrip line, the second microstrip line, the first open stub and the second open stub.

Images