A high rectangular coefficient strip line low pass filter
By employing rectangular waveform microstrip lines and staggered interdigitated microstrip line structures in microwave filters, the rectangular coefficient is optimized, solving the problems of low rectangular coefficient and large size in existing technologies, and achieving high suppression performance and small size design.
Patent Information
- Application Number
- CN202211240255.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-10-11
- Publication Date
- 2026-02-10
- Estimated Expiration
- 2042-10-11
AI Technical Summary
Existing microwave filters have low rectangular coefficients, poor suppression, and are difficult to achieve the required suppression level for components, and they are also relatively large in size.
A rectangular wave-shaped microstrip line is placed between two parallel dielectric substrates. An elliptic function topology is formed by varying the thickness of the convex and concave parts of the wave-shaped microstrip line. Interlaced interdigitated microstrip lines are set up, and the rectangular coefficient is optimized to achieve high suppression and small volume.
It achieves high suppression performance and small size design of the filter, and also features small size, light weight, wide bandwidth, high Q value, and simple and easy-to-implement manufacturing process.
Smart Images
Figure CN115528400B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to the field of radio frequency microwave technology, in particular to a high-rectangular-coefficient strip-line low-pass filter. BACKGROUND
[0002] At present, the filters used in the microwave industry can be divided into microstrip filters, LC filters, dielectric filters and cavity filters. In the microwave product, the filter occupies an important position in the microwave device, and in the microwave assembly, amplifiers, mixers, filters and other components are used in large quantities. Inside the assembly, various types of radio frequency devices are connected in series through microstrip lines, and the microstrip filter is directly processed on the PCB or substrate to produce, which not only reduces the matching loss between the filter and the microstrip line, but also greatly reduces the production cost; however, the ordinary microstrip filter has low rectangular coefficient and low suppression, and it is difficult to achieve the suppression requirement of the assembly. SUMMARY
[0003] In order to solve the above problems of the prior art, the application provides a high-rectangular-coefficient strip-line low-pass filter, which is arranged between two parallel dielectric substrates, and the wave-shaped microstrip line in the rectangular waveform shape is arranged between the two parallel dielectric substrates, the elliptic function topology structure composed of the thick and thin transformation of the convex part and the concave part of the wave-shaped microstrip line, and the staggered arrangement of the interdigital microstrip line are used to optimize the rectangular coefficient, realize the design goal of high suppression, and reduce the volume of the filter.
[0004] In order to achieve the above purpose, the application adopts the following technology:
[0005] A high-rectangular-coefficient strip-line low-pass filter is arranged in a cavity, comprising two parallel dielectric substrates and a strip-line arranged between the two dielectric substrates.
[0006] The strip-line comprises a wave-shaped microstrip line in a rectangular waveform shape, one end of which is connected with an input microstrip line, and the other end of which is connected with an output microstrip line.
[0007] The wave-shaped microstrip line is arranged along the length direction of the dielectric substrate, and comprises continuously staggered convex parts and concave parts, the width of the thick microstrip line at the bottom of the concave part is greater than the width of the thin microstrip line at the top of the convex part.
[0008] Each thick microstrip line is arranged along the width direction and spaced apart from the adjacent thick microstrip line on one side, and the two rows of interdigital microstrip lines between the adjacent two thick microstrip lines are arranged in sequence and cross each other.
[0009] Further, the input microstrip line and the output microstrip line are respectively connected to the outermost thin microstrip line, and each thin microstrip line is arranged on the same length direction straight line with the input microstrip line and the output microstrip line.
[0010] Further, there is a gap between the interdigital microstrip line and the opposite thick microstrip line, and between the interdigital microstrip line and the opposite thick microstrip line.
[0011] Further, the input microstrip line is connected to the signal input end at one end of the cavity, and the output microstrip line is connected to the signal output end at the other end of the cavity.
[0012] The present application has the advantages of:
[0013] The filter of the present application has the characteristics of small volume, light weight, wide frequency band, high Q value, simple process and easy implementation. The wave-shaped microstrip line in the shape of a rectangular wave is arranged between two parallel dielectric substrates, the elliptic function topology structure composed of the obvious thick-thin transformation of the convex part and the concave part of the wave-shaped microstrip line is arranged, and the interdigital microstrip lines arranged alternately are arranged, the rectangular coefficient is optimized, the design goal of high suppression degree is realized, and the volume of the filter can be reduced. BRIEF DESCRIPTION OF DRAWINGS
[0014] Figure 1 is an electromagnetic plane model of the embodiment of the present application.
[0015] Figure 2 is the simulation result of the electromagnetic plane model of the embodiment of the present application.
[0016] Figure 3 is a perspective view of the high rectangular coefficient stripline low-pass filter of the embodiment of the present application.
[0017] Figure 4 is a top view of the high rectangular coefficient stripline low-pass filter of the embodiment of the present application.
[0018] Figure 5 is the simulation result of the high rectangular coefficient stripline low-pass filter of the embodiment of the present application. DETAILED DESCRIPTION
[0019] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the embodiments of the present application will be described in detail below with reference to the drawings, but the described embodiments of the present application are only a part of the embodiments of the present application, not all the embodiments of the present application.
[0020] The embodiment of the present application provides a high rectangular coefficient stripline low-pass filter arranged in a metal cavity, as shown in the figure, which comprises two parallel arranged dielectric substrates 11 and a stripline 2 clamped between the two dielectric substrates 11. Figures 3-4
[0021] In the present example, the dielectric substrate 11 can adopt a Rogers substrate. The stripline 2 comprises a wave-shaped microstrip line 20 in the shape of a rectangular wave, one end of which is connected with an input microstrip line 21, and the other end of which is connected with an output microstrip line 22.
[0022] In this example, the wave-shaped microstrip line 20 is arranged along the length direction of the dielectric substrate 11. As an alternative implementation, according to the actual application requirements, it can also be arranged along the width direction of the dielectric substrate 11, so that the entire strip line 2 is arranged at 90°, and the corresponding input and output ports are also arranged on the other two opposite surfaces of the metal cavity, which can also achieve certain effects.
[0023] In this example, the wave-shaped microstrip line 20 includes concave and convex portions arranged continuously and alternately, the width of the thick microstrip line 24 at the bottom of the concave portion is greater than the width of the thin microstrip line 23 at the top of the convex portion, and the length of the thick microstrip line 24 at the bottom of the concave portion is less than the length of the thin microstrip line 23 at the top of the convex portion. Figure 3 As can be seen, the width of the thick microstrip line 24 is designed to be much greater than the width of the thin microstrip line 23; each thick microstrip line 24 is arranged with a plurality of interdigital microstrip lines 25 along the width direction on one side facing the adjacent thick microstrip line 24, and the two rows of interdigital microstrip lines 25 between the adjacent two thick microstrip lines 24 are arranged alternately and cross each other.
[0024] The input microstrip line 21 and the output microstrip line 22 are respectively connected to the thin microstrip line 23 at the outermost end. The input microstrip line 21 is connected to the signal input end 12 at one end of the cavity, and the output microstrip line 22 is connected to the signal output end 13 at the other end of the cavity.
[0025] Compared with the microstrip filter topology of the prior art, the above scheme of this example utilizes the high Q value characteristics of the strip line / microstrip line itself, and through the shape arrangement of the wave-shaped microstrip line 20, the width arrangement of the thick microstrip line 24 and the thin microstrip line 23 to achieve the alternating of thick and thin, and form the topology structure of the elliptic function; plus the two rows of interdigital microstrip lines 25 arranged alternately and cross each other between the adjacent two thick microstrip lines 24, and the gaps between the interdigital microstrip lines 25 and the thick microstrip lines 24 on the opposite side, and between the interdigital microstrip lines 25 on the thick microstrip lines 24 on the opposite side, to realize the further optimization of the rectangular coefficient, and finally realize the design goal of high suppression index and small volume. The filter realized by the above scheme has the characteristics of small volume, light weight, wide frequency band, high Q value, simple process and easy implementation.
[0026] Specifically, in this example, the interdigital microstrip line 25, the thick microstrip line 24, and the thin microstrip line 23 are arranged in parallel. Each thin microstrip line 23 is on the same length direction straight line with the input microstrip line 21 and the output microstrip line 22. Through the design of this structure, the effect of easier matching with the microwave system can be realized.
[0027] As an alternative, the length of the thick microstrip line 24 at the bottom of the concave portion is less than the length of the thin microstrip line 23 at the top of the convex portion, which can achieve a smaller volume effect.
[0028] As an optional way, the width of the two outermost thick microstrip lines 24 is smaller than the width of the remaining thick microstrip lines 24, which can achieve a higher suppression effect.
[0029] As an optional way, the width of the thin microstrip line 23 and the interdigital microstrip line 25 can be set to be consistent, and the number of interdigital microstrip lines 25 in each column is consistent, such as shown in Figure 4 , each column has 3. Through the design of this structure, the suppression effect can be further improved, and the effect of easier simulation design can be achieved.
[0030] Therefore, there are 6 spaced interdigital microstrip lines 25 between adjacent thick microstrip lines 24, and the gap width of the two nearest adjacent interdigital microstrip lines 25 is close to the width of a single interdigital microstrip line 25, so that from the example shown in Figure 3 , it can be seen that the width of the thick microstrip line 24 is set to be much larger than the width of the thin microstrip line 23, and is about 10 times or more. By setting such a width difference, the distinctness of thick-thin transformation is improved, and the elliptic function topology is better optimized for rectangular coefficients.
[0031] In order to verify the feasibility of the scheme of the present example, a low-pass filter with a cutoff frequency of 4.8 GHz is selected for simulation design, and the index requirements are as follows: working frequency 2GHz~4.8GHz; input and output standing wave ≤1.5; insertion loss ≤1.5dB; out-of-band suppression ratio ≥65dBc@6GHz~10GHz.
[0032] First, according to the working frequency and the difficulty of processing, a suitable dielectric substrate 11 is selected, and the dielectric substrate 11 material is Rogers RO4350 of Rogers; the thickness of the plate material is 20mil (0.508mm).
[0033] Then, a preliminary modeling simulation is performed using the simulation software Genesye, and the electromagnetic plane of the original model is shown in Figure 1 , wherein TL1~TL15 represent the strip microstrip lines, one of TL1, TL15 is the input end, and the other is the output end, TL2, TL5, TL8, TL11, TL14 are connected between TL1 and TL15 in turn and arranged in a straight line, TL2 and TL5 are connected vertically TL3, TL3 is connected to TL4 at the other end, TL5 and TL8 are connected vertically with TL6, TL6 is connected to TL7 at the other end, TL8 and TL11 are connected vertically with TL9, TL9 is connected to TL10, TL11 and TL14 are connected vertically with TL12, TL12 is connected to TL13, and TL10 and TL4 are on the same side, TL13 and TL7 are on the other side, and the corresponding original model simulation result is shown in Figure 2As shown, at 4800MHz, S21 is -4.328dB and S11 is -2.001dB; at 5664MHz, S11 is -107.5e-6dB and S21 is -46.064dB.
[0034] Then, the design was optimized to establish the high rectangular coefficient stripline low-pass filter described in this embodiment.
[0035] Then, according to the performance requirements, the simulation optimization values were set according to the high rectangular coefficient stripline low-pass filter scheme of this embodiment. After simulation optimization, the following results were obtained: Figure 5 The simulation results are shown.
[0036] from Figure 5 It can be seen that within the 2GHz~4.8GHz frequency band, S11 is -19.74dB at 4.8GHz, and after conversion, the VSWR at 4.8GHz is ≤1.15; the worst value of S11 is -16.5dB, and after conversion, the input and output VSWR is ≤1.3; the VSWR of the actual processed product can meet the requirement of ≤1.5.
[0037] The simulated S21 parameters show a maximum loss at 4.8 GHz and a simulated loss of 1.28 dB; the final loss in the actual manufactured product meets the requirement of ≤1.5 dB; the suppression band is ≥76 dBc for the 6 GHz~10 GHz band. Out-of-band suppression is ≥65 dBc.
[0038] Compared to the simulation results of the original electromagnetic plane model ( Figure 2 In this example, the high rectangular coefficient stripline low-pass filter outperforms the original model in terms of standing wave ratio, loss, and suppression ratio. In particular, the suppression ratio is improved by more than 10dB compared to the original model, and the rectangular coefficient is also higher.
[0039] In summary, the high rectangular coefficient stripline low-pass filter design in this example is successful.
[0040] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application also intends to include these modifications and variations.
Claims
1. A high rectangular coefficient stripline low-pass filter, disposed within a cavity, characterized in that, It includes two parallel dielectric substrates (11) and a strip line (2) sandwiched between the two dielectric substrates (11); The stripline (2) includes a waveform microstrip line (20) in the shape of a rectangular wave, one end of which is connected to an input microstrip line (21) and the other end of which is connected to an output microstrip line (22). The waveform microstrip line (20) is arranged along the length direction of the dielectric substrate (11) and includes continuously staggered concave and convex portions. The width of the coarse microstrip line (24) at the bottom of the concave portion is greater than the width of the fine microstrip line (23) at the top of the convex portion. The length of the coarse microstrip line (24) at the bottom of the concave portion is less than the length of the fine microstrip line (23) at the top of the convex portion. The width of the two outermost coarse microstrip lines (24) is less than the width of the remaining coarse microstrip lines (24). Each coarse microstrip line (24) has multiple interdigitated microstrip lines (25) spaced apart along the width direction on the side facing the adjacent coarse microstrip line (24), and the two columns of interdigitated microstrip lines (25) between two adjacent coarse microstrip lines (24) are arranged to cross each other in sequence. Each microstrip line (23) is on the same straight line along the same length direction as the input microstrip line (21) and the output microstrip line (22); Interdigitated microstrip lines (25), coarse microstrip lines (24), and fine microstrip lines (23) are arranged in parallel; There are gaps between the interdigitated microstrip line (25) and the coarse microstrip line (24) on the opposite side, as well as between the interdigitated microstrip line (25) on the coarse microstrip line (24) on the opposite side.
2. The high rectangular coefficient stripline low-pass filter according to claim 1, characterized in that, The input microstrip line (21) and the output microstrip line (22) are connected to the outermost microstrip line (23), respectively.
3. The high rectangular coefficient stripline low-pass filter according to claim 1, characterized in that, The input microstrip line (21) is connected to the signal input terminal (12) located at one end of the cavity, and the output microstrip line (22) is connected to the signal output terminal (13) located at the other end of the cavity.
4. The high rectangular coefficient stripline low-pass filter according to claim 1, characterized in that, The dielectric substrate (11) is a Rogers substrate.
5. The high rectangular coefficient stripline low-pass filter according to claim 1, characterized in that, The widths of the microstrip lines (23) and the interdigitated microstrip lines (25) are the same, and the number of interdigitated microstrip lines (25) in each column is the same.