A microstrip bandpass filter

Abstract

The present application provides a microstrip bandpass filter, including: an impedance gradient hairpin microstrip line, a support structure and a metal plane; the impedance gradient hairpin microstrip line is matched and installed with the outer surface of the support structure; the support structure with the impedance gradient hairpin microstrip line installed is matched and installed with the metal plane; the impedance gradient hairpin microstrip line is used to filter out high-order harmonics on the basis of reducing the parasitic passband frequency; the support structure is used to support the impedance gradient hairpin microstrip line and the metal plane; the metal plane is used as a reference ground plane for the signal in the impedance gradient hairpin microstrip line to reflux the signal in the impedance gradient hairpin microstrip line. In the present application, the above method reduces the interference of the parasitic passband on the filtering of high-order harmonics, thereby improving the effect of suppressing high-order harmonics.

Description

Technical Field

[0001] The present application relates to the field of electronic technology, and in particular to a microstrip line bandpass filter. Background Art

[0002] With the development of modern communication technology, the requirements for the anti-interference ability of communication equipment are getting higher and higher. The role of filters has become particularly important, and the quality of their performance directly affects the communication quality of communication equipment.

[0003] At present, the communication field often uses small-sized and light-weight microstrip linear filters for filtering. However, microstrip linear filters have the problem of poor parasitic passband performance, which makes them unable to suppress high-order harmonics well. Summary of the invention

[0004] In order to solve the above technical problems, the embodiment of the present application provides a microstrip bandpass filter to reduce the interference of the parasitic passband on the filtering of higher harmonics, thereby improving the effect of suppressing higher harmonics. The technical solution is as follows:

[0005] A microstrip bandpass filter comprises: an impedance gradient hairpin type microstrip line, a supporting structure and a metal plane;

[0006] The impedance gradient hairpin microstrip line is matched and installed with the outer surface of the support structure;

[0007] The supporting structure on which the impedance gradient hairpin microstrip line is installed is matched and installed with the metal plane;

[0008] The impedance gradient hairpin microstrip line is used to filter out high-order harmonics on the basis of reducing the parasitic passband frequency;

[0009] The support structure is used to support the impedance gradient hairpin microstrip line and the metal plane;

[0010] The metal plane is used as a reference ground plane for the signal in the impedance gradient hairpin microstrip line to reflux the signal in the impedance gradient hairpin microstrip line.

[0011] Preferably, the impedance gradient hairpin microstrip line is matched and installed with the outer surface of the support structure, comprising:

[0012] The impedance gradient hairpin microstrip line is matched and installed with the upper surface and the lower surface of the supporting structure respectively.

[0013] Preferably, the supporting structure on which the impedance gradient hairpin microstrip line is installed is matched with the metal plane and installed, comprising:

[0014] The lower surface of the supporting structure on which the impedance gradient hairpin microstrip line is installed is matched with the metal plane.

[0015] Preferably, the impedance gradient hairpin microstrip line is a bilaterally symmetrical structure, and the left half and the right half of the impedance gradient hairpin microstrip line both include: a transmission line, a tap line, a first impedance gradient line, a first coupling line, and a second impedance gradient line;

[0016] The transmission line is used to transmit microwave signals;

[0017] The tap line is used to adjust the port matching degree of the microstrip line bandpass filter to reduce signal reflection;

[0018] The first impedance gradient line and the second impedance gradient line are both impedance gradient structures, and are used to eliminate reflection signals generated by impedance discontinuity, and filter out high-order harmonics on the basis of reducing parasitic passband frequencies.

[0019] Preferably, the transmission line has a characteristic impedance of 50Ω and a width of 1.54 mm;

[0020] The tap line has a width of 0.8 mm and a length of 3.59 mm;

[0021] The horizontal plane angle of the first impedance gradient line is 166° and the length is 1.03 mm;

[0022] The first coupling line has a length of 5.77 mm, a width of 0.3 mm, and a spacing of 0.2 mm;

[0023] The horizontal plane angle of the second impedance gradient line is 166° and the length is 1.03 mm.

[0024] Preferably, the impedance gradient hairpin microstrip line is mounted to match the outer surface of the support structure through a copper foil etching process.

[0025] Preferably, the supporting structure is a high-frequency board.

[0026] Preferably, the thickness of the impedance gradient hairpin microstrip line is 0.035 mm;

[0027] The high frequency board is Roers4350B, with a dielectric constant of 3.66 and a thickness of 0.254 mm;

[0028] The metal plane is made of copper foil with a thickness of 0.035 mm.

[0029] Compared with the prior art, the beneficial effects of this application are:

[0030] In the present application, the impedance gradient hairpin microstrip line in the microstrip bandpass filter can filter out high-order harmonics on the basis of reducing the parasitic passband frequency. Since the impedance gradient hairpin microstrip line reduces the parasitic passband frequency, the parasitic passband frequency is kept away from the frequency of high-order harmonics, thereby reducing the interference of the parasitic passband on the filtering of high-order harmonics, thereby improving the effect of suppressing high-order harmonics. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0032] Figure 1 is a schematic top view of a simulation model of a microstrip bandpass filter provided by the present application;

[0033] Figure 2 It is a schematic diagram of a simulation curve of suppressing high-order harmonics by a microstrip bandpass filter provided by the present application;

[0034] Figure 3 It is a schematic diagram of a simulation curve of the passband insertion loss of a microstrip bandpass filter provided by the present application;

[0035] Figure 4 It is a top view of the simulation model of the impedance gradient hairpin microstrip line provided in the present application. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0037] In this embodiment, see Figure 1 , which shows a schematic top view of a simulation model of a microstrip line bandpass filter provided by the present application, such as Figure 1 As shown, the microstrip bandpass filter includes: an impedance gradient hairpin microstrip line 1, a support structure 2 and a metal plane 3.

[0038] The impedance gradient hairpin microstrip line 1 is mounted to match the outer surface of the support structure 2 .

[0039] The support structure 2 on which the impedance gradient hairpin microstrip line 1 is installed is matched with the metal plane 3 .

[0040] The impedance gradient hairpin microstrip line 1 is used to filter out high-order harmonics on the basis of reducing the parasitic passband frequency.

[0041] In this embodiment, the impedance gradient hairpin microstrip line 1 is composed of two transmission lines with different characteristic impedances Z1 and Z2. The total length of the two lines is half a wavelength, and a gradient structure is used at the connection between the two lines with different characteristic impedances to eliminate signal reflection caused by impedance discontinuity. By adjusting the ratio of Z1 / Z2, the parasitic passband frequency can be kept away from the high-order harmonic frequency.

[0042] The support structure 2 is used to support the impedance gradient hairpin microstrip line 1 and the metal plane 3.

[0043] The metal plane 3 is used as a reference ground plane for the signal in the impedance gradient hairpin microstrip line 1 to reflux the signal in the impedance gradient hairpin microstrip line 1 .

[0044] In the present application, the impedance gradient hairpin microstrip line 1 in the microstrip bandpass filter can filter out high-order harmonics on the basis of reducing the parasitic passband frequency. Since the impedance gradient hairpin microstrip line 1 reduces the parasitic passband frequency, the parasitic passband frequency is kept away from the frequency of high-order harmonics, thereby reducing the interference of the parasitic passband on the filtering of high-order harmonics, thereby improving the effect of suppressing high-order harmonics.

[0045] See also Figure 2 , which shows a schematic diagram of the simulation curve of the microstrip bandpass filter suppressing high-order harmonics, such as Figure 2 As shown, m4 is the second harmonic of the operating frequency of 5.83 or 5.84 GHz, and the frequency of this second harmonic is 11.6 GHz; m5 is the third harmonic of the operating frequency of 5.83 or 5.84 GHz, and the frequency of this third harmonic is 17.4 GHz. The waves marked with m1, m2 and m3 are parasitic passbands, and the frequencies of the parasitic passbands are reduced, so that the second harmonic is suppressed by 37 dB and the third harmonic is suppressed by 26 dB, thereby improving the suppression effect of the second and third harmonics.

[0046] At the same time, the microstrip line bandpass filter provided in this embodiment also has the characteristics of small insertion loss in the passband, small size, light weight, low cost, and easy processing.

[0047] See also Figure 3 , which shows a schematic diagram of the simulation curve of the passband insertion loss of the microstrip line bandpass filter, such as Figure 3 As shown, the line indicated by 9 is the filter transmission characteristic S21, the 3dB bandwidth is 5.4GHz-6.4GHz, and the insertion loss is less than 1dB in the 5.6GHz-6.2GHz band; the line indicated by 10 is the filter port return loss S11, and the insertion loss is less than -10dB in the 5.6GHz-6.2GHz band.

[0048] In this embodiment, there are multiple ways to match and install the impedance gradient hairpin microstrip line 1 with the outer surface of the support structure 2, which may include but are not limited to matching and installing the impedance gradient hairpin microstrip line 1 with the upper surface of the support structure 2; or, matching and installing the impedance gradient hairpin microstrip line 1 with the lower surface of the support structure 2; or, matching and installing the impedance gradient hairpin microstrip line 1 with the upper surface and lower surface of the support structure 2 respectively.

[0049] It should be noted that the impedance gradient hairpin microstrip line 1 is matched and installed with the upper surface and the lower surface of the support structure 2 respectively, which means that the upper surface and the lower surface of the support structure 2 are matched and installed with the impedance gradient hairpin microstrip line 1. This installation method increases the number of impedance gradient hairpin microstrip lines 1, and the effect of filtering out high-order harmonics is better.

[0050] In the present embodiment, based on the manner in which the impedance gradient hairpin microstrip line 1 is respectively matched and installed with the upper surface and the lower surface of the support structure 2, the matching installation of the support structure 2 on which the impedance gradient hairpin microstrip line 1 is installed and the metal plane 3 may specifically include but is not limited to the matching installation of the lower surface of the support structure 2 on which the impedance gradient hairpin microstrip line 1 is installed and the metal plane 3.

[0051] In another embodiment of the present application, the specific structure of the impedance gradient hairpin type microstrip line 1 is introduced, see Figure 4 , which shows a top view of the simulation model of the impedance gradient hairpin microstrip line 1, as shown Figure 4 As shown, the impedance gradient hairpin microstrip line 1 is a bilaterally symmetrical structure, and the left and right halves of the impedance gradient hairpin microstrip line 1 both include: a transmission line 11, a tap line 12, a first impedance gradient line 13, a first coupling line 14, and a second impedance gradient line 15.

[0052] The transmission line 11 is used to transmit microwave signals.

[0053] The tap line 12 is used to adjust the port matching degree of the microstrip line bandpass filter to reduce signal reflection.

[0054] The first impedance gradient line 13 and the second impedance gradient line 15 are both impedance gradient structures, and are used to eliminate the reflected signal generated by impedance discontinuity, and filter out high-order harmonics on the basis of reducing the parasitic passband frequency.

[0055] In this embodiment, the specific structures of the transmission line 11, the tap line 12, the first impedance gradient line 13, the first coupling line 14 and the second impedance gradient line 15 are introduced as follows:

[0056] The transmission line 11 has a characteristic impedance of 50Ω and a width of 1.54mm;

[0057] The tap line 12 has a width of 0.8 mm and a length of 3.59 mm;

[0058] The horizontal plane angle of the first impedance gradient line 13 is 166° and the length is 1.03 mm;

[0059] The first coupling line 14 has a length of 5.77 mm, a width of 0.3 mm, and a spacing of 0.2 mm;

[0060] The horizontal plane angle of the second impedance gradient line 15 is 166° and the length is 1.03 mm.

[0061] It should be noted that the specific structure of the transmission line 11, the tap line 12, the first impedance gradient line 13, the first coupling line 14 and the second impedance gradient line 15 is not limited to the structure illustrated in this embodiment, and the specific structure of the transmission line 11, the tap line 12, the first impedance gradient line 13, the first coupling line 14 and the second impedance gradient line 15 can be adjusted according to actual needs.

[0062] In another embodiment of the present application, the installation process of the impedance gradient hairpin microstrip line 1 is introduced as follows:

[0063] The impedance gradient hairpin microstrip line 1 is matched and installed with the outer surface of the support structure 2 through a copper foil etching process.

[0064] The impedance gradient hairpin microstrip line 1 may also be mounted to match the outer surface of the support structure 2 through other processes, which are not limited here.

[0065] In this embodiment, the support structure 2 may specifically include but is not limited to a high-frequency board.

[0066] In the above-mentioned microstrip bandpass filter, the thickness of the impedance gradient hairpin microstrip line 1 is 0.035 mm;

[0067] The high frequency board is Roers4350B, with a dielectric constant of 3.66 and a thickness of 0.254 mm;

[0068] The metal plane 3 is made of copper foil and has a thickness of 0.035 mm.

[0069] It should be noted that each embodiment in this specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other. For the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0070] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0071] The above is a detailed introduction to a microstrip bandpass filter provided by the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. At the same time, for general technicians in this field, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A microstrip bandpass filter, characterized in that: include: Impedance gradient hairpin microstrip lines, support structures and metal planes; The impedance gradient hairpin microstrip line is matched and installed on the upper surface of the support structure; The lower surface of the support structure is matched and installed with the metal plane; The impedance gradient hairpin microstrip line is used to filter out high-order harmonics on the basis of reducing the parasitic passband frequency; The support structure is used to support the impedance gradient hairpin microstrip line and the metal plane; The metal plane is used as a reference ground plane for the signal in the impedance gradient hairpin microstrip line to reflux the signal in the impedance gradient hairpin microstrip line; The impedance gradient hairpin microstrip line is a bilaterally symmetrical structure, and the left and right halves of the impedance gradient hairpin microstrip line both include: a transmission line, a tap line, a first impedance gradient line, a first coupling line, and a second impedance gradient line; The transmission line is used to transmit microwave signals; The tap line is used to adjust the port matching degree of the microstrip line bandpass filter to reduce signal reflection; The first impedance gradient line and the second impedance gradient line are both continuous impedance gradient structures, and the horizontal plane angles are both 166°, and are both used to eliminate the reflected signals generated by impedance discontinuity and filter out high-order harmonics on the basis of reducing the parasitic passband frequency.

2. The microstrip line bandpass filter according to claim 1, characterized in that: The transmission line has a characteristic impedance of 50Ω and a width of 1.54mm; The tap line has a width of 0.8 mm and a length of 3.59 mm; The length of the first impedance gradient line is 1.03 mm; The first coupling line has a length of 5.77 mm, a width of 0.3 mm, and a spacing of 0.2 mm; The length of the second impedance gradient line is 1.03 mm.

3. The microstrip line bandpass filter according to claim 1, characterized in that: The impedance gradient hairpin microstrip line is matched and installed with the outer surface of the supporting structure through a copper foil etching process.

4. The microstrip line bandpass filter according to claim 3, characterized in that: The supporting structure is a high-frequency board.

5. The microstrip line bandpass filter according to claim 4, characterized in that: The thickness of the impedance gradient hairpin microstrip line is 0.035 mm; The high frequency board is Roers4350B, with a dielectric constant of 3.66 and a thickness of 0.254 mm; The metal plane is made of copper foil with a thickness of 0.035 mm.

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