Topological structure and high-selectivity miniaturized broadband band-pass filter

Abstract

The utility model discloses a topological structure, which comprises three parallel lines, a microstrip line, an open-circuit branch knot, an input port and an output port, one end of the three parallel lines is respectively connected with the input port and the output port, and the other end of the three parallel lines is sequentially connected with the microstrip line and the open-circuit branch knot. The utility model further discloses a high-selectivity miniaturized broadband band-pass filter based on the topological structure. The high-selectivity miniaturized broadband band-pass filter has the advantages of high selectivity and small size.

Description

TECHNICAL FIELD

[0001] The utility model relates to filter technical field especially relates to a topology structure and miniaturized wideband band pass filter of high selectivity. BACKGROUND

[0002] With the rapid development of modern wireless communication technology, the contradiction between limited spectrum resources and growing information transmission demand is increasingly intense, various communication systems and communication modes are more and more close to each other even stagger in frequency space, which brings great challenge to the anti-interference ability of each communication system to other system.In addition, with the increasing integration density of future radio frequency devices, the miniaturization of devices is the inevitable trend of future device and microwave system development.Under this background, the high selectivity and miniaturization of wideband filter have very high scientific research and commercial value, which attracts the attention of scholars and engineers.However, the existing wideband band pass filter often cannot meet the characteristics of high selectivity and miniaturization at the same time, which seriously affects its use in modern wireless communication system. SUMMARY

[0003] In view of the above shortcomings of the prior art, the main purpose of the utility model is to provide a topology structure and miniaturized wideband band pass filter of high selectivity, aiming at solving the problems of poor selectivity and large size of the existing wideband band pass filter.

[0004] In order to solve the above technical problems, the utility model adopts the technical scheme that:

[0005] A topology structure, comprising parallel three lines, microstrip lines, open circuit branches, input ports and output ports, one end of the parallel three lines is connected with the input port and the output port respectively, and the other end of the parallel three lines is connected with the microstrip lines and the open circuit branches in turn.

[0006] Optionally, the parallel three lines are composed of three parallel transmission lines, the transmission lines have oppositely arranged first ends and second ends, the first ends of the transmission lines on both sides are connected with the input port and the output port one by one, and the second end of the transmission line in the middle is connected with the microstrip lines and the open circuit branches in turn.

[0007] Optionally, the parallel three lines are parallel to the open circuit branches and perpendicular to the microstrip lines.

[0008] Optionally, the open circuit branches extend towards the direction close to the parallel three lines.

[0009] Optionally, the electrical length of the parallel three lines is one quarter of the corresponding wavelength based on the center frequency of the topology structure of the band pass filter.

[0010] Optionally, the sum of the electrical length of the microstrip line and the electrical length of the open-circuit stub is a corresponding quarter wavelength at a center frequency of the bandpass filter based on the topology.

[0011] Optionally, the characteristic impedance of the microstrip line is equal to the characteristic impedance of the open-circuit stub.

[0012] Another technical solution adopted by the utility model is:

[0013] A high-selectivity miniaturized wideband bandpass filter comprises the above topology.

[0014] Optionally, the topology is arranged on a circuit board, and 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 11.7 mm*3.9 mm.

[0015] Optionally, the parallel three-wire line is composed of three parallel transmission lines, and the specific parameters on the circuit board are as follows:

[0016] L T = 8.0 mm, L T represents the physical length of the transmission line;

[0017] S T = 0.1 mm, S T represents the spacing between the two adjacent transmission lines;

[0018] W T = 0.2 mm, W T represents the physical width of the transmission line;

[0019] L1 = 2.6 mm, L1 represents the physical length of the microstrip line;

[0020] L2 = 3.8 mm, L2 represents the physical length of the open-circuit stub;

[0021] W1 = 0.7 mm, W1 represents the physical width of the microstrip line and the physical width of the open-circuit stub.

[0022] The utility model discloses the beneficial effect lies in: a new topology structure is proposed, and a wideband bandpass filter can be designed based on the topology structure, which has the advantages of high selectivity and miniaturization. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Fig. 1 shows a topology structure schematic diagram of an embodiment of the utility model;

[0024] Figure 2 Fig. 2 shows an equivalent topology structure schematic diagram of the topology structure of the embodiment of the utility model.

[0025] Figure 3 Figure 8 shows a schematic diagram of an odd mode form of an equivalent topology structure according to an embodiment of the present application;

[0026] Figure 4 Figure 9 shows a schematic diagram of an even mode form of an equivalent topology structure according to an embodiment of the present application;

[0027] Figure 5 Figure 10 shows a layout plot of a high-selectivity miniaturized wideband bandpass filter according to an embodiment of the present application;

[0028] Figure 6 Figure 11 shows a S-parameter simulation result of a high-selectivity miniaturized wideband bandpass filter according to an embodiment of the present application. DETAILED DESCRIPTION

[0029] In order to more clearly understand the technical content, the purposes and effects of the present application, the present application is described in detail below in combination with specific embodiments and the accompanying drawings. It should be noted that the embodiments and the features in the embodiments of the present application can be combined with each other without conflict. In the following description, a large number of specific details are set forth in order to fully understand the present application, and the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0030] Please refer to Figures 1-4 Figure 1 shows an embodiment of the present application.

[0031] A topology structure, as shown in Figure 2, comprises a parallel three-wire, a microstrip line, an open stub, an input port and an output port. Figure 1 The parallel three-wire is composed of three parallel transmission lines, the transmission lines have oppositely arranged first ends and second ends, the first ends of the transmission lines on both sides are respectively connected to the input port and the output port one by one, and the second end of the transmission line in the middle is sequentially connected to the microstrip line and the open stub.

[0032] The parallel three-wire is parallel to the open stub and perpendicular to the microstrip line. The open stub extends towards the direction close to the parallel three-wire.

[0033] The electrical length of the parallel three-wire is a quarter wavelength corresponding to the center frequency of the bandpass filter based on the topology structure. The sum of the electrical length of the microstrip line and the electrical length of the open stub is a quarter wavelength corresponding to the center frequency of the bandpass filter based on the topology structure.

[0034] The characteristic impedance of the microstrip line is equal to the characteristic impedance of the open stub.

[0035] To facilitate the analysis of the performance of this topology, such as Figure 2 The diagram shows the equivalent topology of this topology.

[0036] In the equivalent topology, the odd-mode characteristic impedance of the first parallel line and the odd-mode characteristic impedance of the second parallel line are Z. oo The even-mode characteristic impedance of the first parallel line and the even-mode characteristic impedance of the second parallel line are Z. oe The characteristic impedance of the first microstrip line is Z1, and the characteristic impedances of the second microstrip line and the first open-circuit stub are Z2. The electrical lengths of the first parallel line, the second parallel line, and the first microstrip line are equal, each being a quarter wavelength corresponding to the center frequency of the bandpass filter based on the aforementioned topology. The sum of the electrical lengths of the second microstrip line and the first open-circuit stub is also a quarter wavelength corresponding to the center frequency of the bandpass filter based on the aforementioned topology.

[0037] Since the equivalent topology is symmetrical, its transmission poles can be analyzed using even and odd modes. For example... Figure 3 The figure shows the odd-mode form of the equivalent topology.

[0038] When Y ino When f = 0, it can be concluded that this topology has an odd-mode transmission pole. When f0 is the center frequency of the bandpass filter based on the above topology, the frequencies corresponding to the odd-mode transmission pole are as follows:

[0039] f op1 =f0

[0040] like Figure 4 The figure shows the even-mode form of the equivalent topology, where the electrical length of the third microstrip line is a quarter wavelength at the center frequency of the bandpass filter based on the topology, and the characteristic impedance of the third microstrip line is twice that of the first microstrip line.

[0041] When Y inoL +Y inoR When f = 0, it can be concluded that this topology has three even-mode transmission poles. When f0 is the center frequency of the bandpass filter based on this topology, the frequencies corresponding to the three even-mode transmission poles are as follows:

[0042]

[0043] f ep2 =f0

[0044]

[0045] For this topology, its transmission zero can be calculated by the following method: multiply the ABCD matrix of the cascaded resonator constituting the topology in turn to obtain the ABCD matrix corresponding to the topology; convert the ABCD matrix of the topology into the corresponding S matrix. When |S 21 | = 0, it can be obtained that this topology has five transmission points, and the frequencies corresponding to the five transmission zeros are respectively:

[0046] f z1 = 0

[0047]

[0048]

[0049] f z4 = 2f0

[0050]

[0051] From the above analysis, the equivalent topology has one odd-mode transmission pole, three even-mode transmission poles, and five transmission zeros. Regardless of how the values of the parameters Z oo , Z oe , Z1 and Z2 change, the relative positions of these transmission zero-poles, i.e. z1 < f z2 < f ep1 < f op1 = f ep2 < f ep3 < f z3 < f z4 < f z5 , are not changed. Therefore, the radio frequency filter designed based on this topology can only be a band-pass filter, which has three transmission poles in the passband to ensure the flatness of the passband, and has five transmission zeros in the stopband to ensure the high selectivity and wide stopband of the edge band.

[0052] Please refer to Figure 5 and 6 , the second embodiment of the utility model is:

[0053] A high-selectivity small-size wideband band-pass filter, comprising the topology and the circuit board of the first embodiment, the topology is arranged 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 11.7 mm*3.9 mm.

[0054] As Figure 5 shown, the specific parameter settings on the circuit board are:

[0055] L T= 8.0 mm, L T represents the physical length of the transmission line;

[0056] S T = 0.1 mm, S T represents the spacing between two adjacent transmission lines;

[0057] W T = 0.2 mm, W T represents the physical width of the transmission line;

[0058] L1 = 2.6 mm, L1 represents the physical length of the microstrip line;

[0059] L2 = 3.8 mm, L2 represents the physical length of the open-circuit stub;

[0060] W1 = 0.7 mm, W1 represents the physical width of the microstrip line and the physical width of the open-circuit stub.

[0061] The S-parameter simulation results of the high-selectivity miniaturized wideband bandpass filter of the embodiment are shown in Fig. 6. Figure 6 The passband bandwidth range with a reflection coefficient less than -10 dB is 4.49-7.33 GHz, the center frequency of the passband is 5.91 GHz, the absolute bandwidth is 2.84 GHz, and the relative bandwidth is 48.1%. In addition, there are three transmission poles in the passband range, which are located at 4.85, 5.96, and 7.07 GHz, respectively. The three transmission poles ensure the characteristics of low insertion loss and high flatness in the passband.

[0062] The stopband range with an isolation greater than 20 dB is 0-3.57 GHz and 8.05-12.00 GHz. In the first stopband, there are two transmission zeros, which are located at 0 and 3.3 GHz, respectively; in the second stopband, there are three transmission zeros, which are located at 8.3 GHz, 10.48 GHz, and 11.56 GHz, respectively. The five transmission zeros not only determine the high selectivity of the filter sideband, but also ensure the high isolation in the wide stopband of the filter.

[0063] In summary, the topology structure proposed by the present application can be used to design a wideband bandpass filter. The high-selectivity miniaturized wideband bandpass filter designed based on the topology structure not only ensures the characteristics of low insertion loss, high flatness, and high isolation, but also has the advantages of high selectivity and small size.

[0064] The above description is only an embodiment of the present application, and does not limit the patent range of the present application, so any modification, equivalent change, and modification made to the above embodiment according to the technical essence of the present application still belongs to the range of the technical solution of the present application.

Claims

1. A topological structure, characterized in that, The filter includes a parallel tri-line, a microstrip line, an open-circuit stub, an input port, and an output port. One end of the parallel tri-line is connected to the input port and the output port, respectively. The other end of the parallel tri-line is connected to the microstrip line and the open-circuit stub in sequence. The parallel tri-line is parallel to the open-circuit stub and perpendicular to the microstrip line. The electrical length of the parallel tri-line is one-quarter wavelength corresponding to the center frequency of the bandpass filter based on the topology. The sum of the electrical length of the microstrip line and the electrical length of the open-circuit stub is one-quarter wavelength corresponding to the center frequency of the bandpass filter based on the topology.

2. The topology according to claim 1, characterized in that, The parallel tri-line consists of three parallel transmission lines. Each transmission line has a first end and a second end that are positioned opposite each other. The first ends of the transmission lines on both sides are connected to the input port and the output port respectively, and the second end of the transmission line in the middle is connected to the microstrip line and the open stub in sequence.

3. The topology according to claim 1, characterized in that, The open branch extends toward the direction of the parallel three lines.

4. The topology according to claim 1, characterized in that, The characteristic impedance of the microstrip line is equal to the characteristic impedance of the open stub.

5. A highly selective, miniaturized broadband bandpass filter, characterized in that, Includes the topology described in any one of claims 1-4.

6. The highly selective miniaturized broadband bandpass filter according to claim 5, characterized in that, It also includes a circuit board, on which the topology is disposed. The circuit board has a dielectric constant of 3.38, a dielectric loss of 0.0022, a thickness of 0.813 mm, and dimensions of 11.7 mm * 3.9 mm.

7. The highly selective miniaturized broadband bandpass filter according to claim 6, characterized in that, The parallel tri-line consists of three parallel transmission lines, and the specific parameters on the circuit board are set as follows: L T =8.0mm, L T Indicates the physical length of the transmission line; S T =0.1mm, S T This indicates the spacing between two adjacent transmission lines; W T =0.2mm, W T This indicates the physical width of the transmission line; L1 = 2.6 mm, where L1 represents the physical length of the microstrip line; L2 = 3.8 mm, where L2 represents the physical length of the open branch; W1 = 0.7 mm, where W1 represents the physical width of the microstrip line and the physical width of the open stub.

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