A UWB stripline bandpass filter

Abstract

An ultra-wideband stripline bandpass filter, comprising: a pair of dielectric substrates, in which a plurality of strip-shaped gaps are formed by inward depressions from one side wall, the strip-shaped gaps penetrate the top and bottom surfaces of the dielectric substrates, and the strip-shaped gaps divide a region on one side of the dielectric substrates into a plurality of branch platforms; a stripline unit, clamped between the pair of dielectric substrates, including a strip-shaped input end, a strip-shaped output end, a stripline connected between the strip-shaped input end and the strip-shaped output end, and branch lines disposed in each branch platform; the stripline is folded and routed in a rectangular waveform, the wave peaks thereof protrude towards the other side of the dielectric substrate, the number of wave peaks is the same as the number of strip-shaped gaps, the positions of the wave peaks correspond to the strip-shaped gaps, one end of each branch line is connected to the wave valley of the stripline, the other end extends a predetermined length in the branch platform, and the extending end is connected to the top and bottom surfaces of the dielectric substrate through metallized vias to be grounded. Ultra-wideband and high out-of-band rejection characteristics are achieved by direct coupling, with a large coupling coefficient, a small volume, and a small in-band insertion loss.

Description

Technical Field

[0001] This application belongs to the field of radio frequency and microwave technology, relates to transmission line filters, and particularly relates to an ultra-wideband stripline bandpass filter for realizing radio wave frequency selection. Background Art

[0002] With the continuous emergence and development of new materials, the design of filters has evolved from the initial LC filters to waveguide filters and coaxial filters. With the advent of planar transmission lines, such transmission lines have been widely used to design filters, such as microstrip filters, stripline filters, coplanar waveguide filters, etc.

[0003] Currently, most bandpass filters are in the form of microstrip lines, and generally use electrical coupling and magnetic coupling methods for energy transmission. In this way, a large coupling coefficient cannot be achieved. Summary of the Invention

[0004] To solve the above deficiencies of the prior art, this application provides an ultra-wideband stripline bandpass filter. Through the direct coupling method of resonators, it realizes ultra-wideband and high out-of-band rejection characteristics. It can not only obtain a large coupling coefficient, but also achieve small in-band insertion loss through the direct coupling method of striplines while minimizing the volume.

[0005] To achieve the above object, the present invention adopts the following technologies:

[0006] An ultra-wideband stripline bandpass filter, comprising:

[0007] A pair of dielectric substrates arranged in parallel, with a signal input port at one end and a signal output port at the other end. The dielectric substrates are recessed inward from one side wall to form a plurality of strip-shaped gaps. The strip-shaped gaps are arranged at intervals and penetrate through the top and bottom surfaces of the dielectric substrates. The strip-shaped gaps divide one side area of the dielectric substrates into a plurality of branch platforms;

[0008] A stripline unit, sandwiched between a pair of dielectric substrates, includes a strip-shaped input end connected to the signal input port, a strip-shaped output end connected to the signal output port, a stripline connected between the strip-shaped input end and the strip-shaped output end, and branch lines arranged in each branch platform;

[0009] Wherein, the stripline folds and runs in a rectangular waveform, with its wave peaks protruding towards the other side of the dielectric substrate. The number of wave peaks is the same as the number of strip-shaped gaps, and the positions of the wave peaks correspond to the strip-shaped gaps. One end of the branch line is connected to the wave valley of the stripline, and the other end extends a predetermined length within the branch platform, and the extended end is grounded through a metallized via hole connecting the top and bottom surfaces of the dielectric substrate.

[0010] Wherein, each branch platform and its corresponding branch line, metallized via hole, and section of the stripline form a resonator coupling unit.

[0011] Further, from the strip input end and the strip output end towards the middle direction, the width of the branch line increases successively, and the length decreases successively.

[0012] Further, the trough at the starting end of the strip line is connected to the strip input end, and the trough at the ending end is connected to the strip output end. The strip input end and the strip output end are in the same straight line as the trough.

[0013] Further, the length direction of the branch line is consistent with the length direction of the strip gap. There is a predetermined distance between the trough of the strip line and the inner end wall of the strip gap. The inner width of the crest of the strip line is greater than the width of the strip gap, and the inner width of the trough is greater than the width of the branch line and less than the width of the branch platform.

[0014] The beneficial effects of the present invention are as follows:

[0015] 1. By directly coupling in the way of sandwiching a strip line unit between a pair of parallel dielectric substrates, a large coupling coefficient can be obtained, and small in-band insertion loss can be achieved;

[0016] 2. By setting a strip gap on the dielectric substrate and forming a branch platform, combining a rectangular waveform strip line with folded traces and a branch line extending into the branch platform, multiple resonant units are formed, realizing ultra-wideband and high out-of-band rejection characteristics;

[0017] 3. By adopting such an arrangement form of the strip line with folded traces, in cooperation with the strip gap and the branch platform structure, a small planar volume can be achieved; the upper and lower parts of the strip line are shielded by ground, with good electromagnetic compatibility and high suppression. Description of the Drawings

[0018] Figure 1 is a three-dimensional view of the overall structure of the ultra-wideband strip line bandpass filter according to the embodiment of the present application.

[0019] Figure 2 is a three-dimensional view of the strip line unit of the ultra-wideband strip line bandpass filter according to the embodiment of the present application.

[0020] Figure 3 is a three-dimensional perspective view of the overall structure of the ultra-wideband strip line bandpass filter according to the embodiment of the present application.

[0021] Figure 4 is a top perspective view of the overall structure of the ultra-wideband strip line bandpass filter according to the embodiment of the present application.

[0022] Figure 5 is the simulation result of the ultra-wideband strip line bandpass filter according to the embodiment of the present application. Detailed Embodiments

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will describe the embodiments of the present invention in detail with reference to the accompanying drawings. However, the embodiments described herein are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0024] An embodiment of the present application provides an ultra-wideband stripline bandpass filter, as Figures 1 to 4 shown, disposed in a metal cavity, including a pair of parallel dielectric substrates 1 and a stripline unit 2 sandwiched between the pair of dielectric substrates 1.

[0025] In this example, as Figure 1 、 Figure 3 shown, one end of the pair of dielectric substrates 1 is provided with a signal input port 13, and the other end is provided with a signal output port 14.

[0026] In this example, as Figure 1 、 Figures 3 to 4 shown, the pair of dielectric substrates 1 are recessed inward from one side wall to form a plurality of strip-shaped gaps 11. The strip-shaped gaps 11 are arranged at intervals and penetrate through the top surface and the bottom surface of the dielectric substrate 1. The strip-shaped gaps 11 divide one side area of the dielectric substrate 1 into a plurality of branch platforms 12.

[0027] In this example, as Figures 2 to 4 shown, the stripline unit 2 includes a stripline 23 and strip-shaped input ends 21 and strip-shaped output ends 22 connected to both ends (starting end and ending end) thereof, and branch lines 24 disposed in each branch platform 12. The strip-shaped input end 21 is connected to the signal input port 13, and the strip-shaped output end 22 is connected to the signal output port 14.

[0028] As Figure 2 、 Figure 4 shown, the stripline 23 adopted in this example is of a folded trace type and has a rectangular waveform. Its wave peaks protrude toward the other side of the dielectric substrate 1. The number of wave peaks is the same as the number of strip-shaped gaps 11, and the positions of the wave peaks correspond to the strip-shaped gaps 11. One end of the branch line 24 is connected to the wave valley of the stripline 23, and the other end extends a predetermined length in the branch platform 12, and the extending end is grounded through a metallized via 20 that connects the top surface and the bottom surface of the dielectric substrate 1. Among them, the wave valley at the starting end of the stripline 23 is connected to the strip-shaped input end 21, and the wave valley at the ending end is connected to the strip-shaped output end 22. Optionally, the strip-shaped input end 21 and the strip-shaped output end 22 are in the same straight line as the wave valley.

[0029] Each branch platform 12 and its corresponding branch line 24, metallized via 20, and the section of the stripline 23 form a resonant coupling unit, thereby forming a plurality of grid-shaped periodic resonant coupling units.

[0030] The grid-shaped periodic resonant coupling unit of this example can disrupt the current distribution and change the characteristics of the transmission line, capable of suppressing the propagation of electromagnetic waves of some frequencies in the structure; the multi-stage resonant coupling unit changes the original equivalent dielectric constant, and the corresponding distributed capacitance and distributed inductance both change accordingly, realizing the advantages of miniaturization, slow-wave characteristics, high-pass band-stop, etc. of the transmission line.

[0031] Specifically, from the strip input end 21 and the strip output end 22 towards the middle direction, the width of the branch line 24 increases successively, and the length decreases successively. This setting method of shape change realizes the technical effects of ultra-wideband and high suppression ratio.

[0032] As an optional specific implementation solution, the length direction of the branch line 24 is the same as the length direction of the strip gap 11. There is a predetermined distance between the trough of the strip line 23 and the inner end wall of the strip gap 11. The inner width of the peak of the strip line 23 is greater than the width of the strip gap 11, and the inner width of the trough is greater than the width of the branch line 24 and less than the width of the branch platform 12. Through these direction definitions, size control, and distance settings, the... technical effects can be achieved.

[0033] The following indicators are required to be met:

[0034] 1. Passband range: 6 GHz to 18 GHz;

[0035] 2. Input and output standing wave: ≤1.5;

[0036] 3. Insertion loss: ≤2 dB;

[0037] 4. Out-of-band rejection: ≥50 dBc @ 5 GHz & ≥60 dBc @ 20 GHz.

[0038] Adopt the solution of this example for implementation. Specifically, as Figures 1 to 4 , use 9 resonant coupling units, arrange them in the strip line folding routing manner described in the previous example. The dielectric substrate 1 uses Rogers RT5880, with a thickness of 0.508 mm. The strip line unit 2 uses copper foil, and perform modeling and simulation to obtain the simulation results as Figure 5 shown.

[0039] From Figure 5 the shown simulation structure, it can be seen that:

[0040] 1. The filter can cover 6 GHz to 18 GHz;

[0041] 2. The worst in-band return loss is -20 dBc. After conversion, the standing wave can meet ≤1.5;

[0042] 3. The worst value of the insertion loss at the filter sideband is 1.8 dB;

[0043] 4. The out-of-band rejection is -55 dBc at 5 GHz and less than -70 dBc at 20 GHz.

[0044] It shows that the ultra-wideband stripline bandpass filter designed according to this example can meet the specified index requirements.

[0045] The above are only the preferred embodiments of the present application and are not used to limit the present application. Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application is also intended to include these modifications and variations.

Claims

1. An ultra-wideband stripline bandpass filter, characterized in that, Comprising: A pair of parallel dielectric substrates (1), with a signal input port (13) provided at one end and a signal output port (14) provided at the other end. A plurality of strip-shaped gaps (11) are formed by inward depression from the outer wall on the same side of the pair of dielectric substrates (1). The strip-shaped gaps (11) are arranged at intervals and penetrate through the top and bottom surfaces of the pair of dielectric substrates (1). The strip-shaped gaps (11) divide the area of the dielectric substrate (1) on their respective sides into a plurality of branch platforms (12); A strip line unit (2), clamped between the pair of dielectric substrates (1), including a strip-shaped input end (21) connected to the signal input port (13), a strip-shaped output end (22) connected to the signal output port (14), a strip line (23) connected between the strip-shaped input end (21) and the strip-shaped output end (22), and branch lines (24) provided in each branch platform (12); Wherein, the strip line (23) has a folded trace and is in a rectangular waveform. Its wave peaks protrude towards the other side of the dielectric substrate (1) opposite to the side where the strip-shaped gap (11) is located. The number of wave peaks is the same as the number of strip-shaped gaps (11), and the positions of the wave peaks correspond to the strip-shaped gaps (11). One end of the branch line (24) is connected to the wave valley of the strip line (23), and the other end extends a predetermined length within the branch platform (12), and the extended end is connected to the top and bottom surfaces of the dielectric substrate (1) through a metallized via (20) to be grounded.

2. The ultra-wideband stripline bandpass filter according to claim 1, characterized in that, Each branch platform (12) and the corresponding section of the branch line (24), the metallized via (20), and the strip line (23) constitute a resonant coupling unit (3).

3. The ultra-wideband stripline bandpass filter according to claim 1, characterized in that, From the strip-shaped input end (21) and the strip-shaped output end (22) towards the middle direction, the width of the branch line (24) increases successively, and the length decreases successively.

4. The ultra-wideband stripline bandpass filter according to claim 1, characterized in that, The wave valley at the starting end of the strip line (23) is connected to the strip-shaped input end (21), and the wave valley at the end is connected to the strip-shaped output end (22).

5. The ultra-wideband stripline bandpass filter according to claim 1, characterized in that, The length direction of the branch line (24) is the same as the length direction of the strip-shaped gap (11).

6. The ultra-wideband stripline bandpass filter according to claim 1, characterized in that, There is a predetermined distance between the wave valley of the strip line (23) and the inner end wall of the strip-shaped gap (11).

7. The ultra-wideband stripline bandpass filter according to claim 1, characterized in that, The inner width of the wave peak of the strip line (23) is greater than the width of the strip-shaped gap (11), and the inner width of the wave valley is greater than the width of the branch line (24) and less than the width of the branch platform (12).

8. The ultra-wideband stripline bandpass filter according to claim 1, characterized in that, The filter is arranged in a metal cavity.

9. The ultra-wideband stripline bandpass filter according to claim 1, characterized in that, The dielectric substrate (1) uses Rogers RT5880.

10. The ultra-wideband stripline bandpass filter according to claim 1, characterized in that, The strip line unit (2) uses copper foil.

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