A low-pass harmonic suppression filter

Abstract

This solution discloses a low-pass harmonic suppression filter, which is provided with six filter cavities. The upper and lower surfaces of each filter cavity are provided with multiple metal pillars arranged at equal distances. The height b of the first filter cavity is 1. c1 , height b of the second filter cavity c2 , the third filter cavity height b c3 , the fourth filter cavity height b c4 , the fifth filter cavity height b c5 and the height b of the sixth filter cavity c6 Satisfies: b c1 =b c6 >b c2 =b c5 >b c3 =b c4 , the first metal column height b k1 , height b of the second metal column k2 , height b of the third metal column k3 , the fourth metal pillar height b k4 , the fifth metal pillar height b k5 and the sixth metal pillar height b k6 Satisfy: (b c1 -2b k1 )=(b c6 -2b k6 )>(b c2 -2b k2 )=(b c5 -2b k5 )>(b c3 -2b k3 )=(b c4 -2b k4 ), the length of the first metal column d k1 , the length of the second metal column d k2 , length of the third metal column d k3 , length of the fourth metal column d k4 , the length of the fifth metal column d k5 and the sixth metal pillar length d k6 Satisfaction: d k1 =d k6 <d k2 =d k5 <d k3 =d k4 , which enables the filter to achieve wide operating frequency band, high harmonic suppression and wide harmonic suppression band at the same time.

Description

Technical Field

[0001] The present invention belongs to the field of signal processing technology, and specifically relates to a low-pass harmonic suppression filter. Background Art

[0002] In the design and operation of high-power systems, the characteristics of the system's output signal are crucial considerations. High-power signals not only carry the system's required operating frequency band but are often accompanied by a series of high-power harmonic signals. While these harmonic signals, such as second- and third-order modes, are not directly required by the system, their high output power can pose a potential threat to normal operation. To ensure stable and reliable system performance, effective measures must be taken to filter out these harmonic signals. Harmonic suppression filters, as the primary instrument for this task, are of paramount importance.

[0003] The working principle of harmonic suppression filters is their ability to identify and filter out non-operating frequency components, specifically high-power harmonic signals, from signals. In practical applications, filters vary in type and structure to meet the needs of different systems. Microstrip and waveguide harmonic suppression filters are two of the more common types. Microstrip filters are widely used in certain applications due to their compact size and ease of fabrication. However, for high-power systems, microstrip lines have limited power capacity and relatively high transmission losses, limiting their potential for application in high-power environments. In contrast, waveguide harmonic suppression filters, while slightly larger in size, offer low transmission losses and high power capacity, making them an ideal choice for high-power systems. Placing a waveguide harmonic suppression filter at the final stage of a system's output not only ensures maximum output of signals within the operating frequency band, but also effectively suppresses high-power second and third harmonics, thereby ensuring stable system operation.

[0004] However, even waveguide harmonic suppression filters face many challenges in design and application. Figure 1As shown in the figure, harmonic suppression is achieved by arranging metal pillars of uniform size at equal intervals. Although this method can achieve harmonic suppression to a certain extent, it often lacks the ability to suppress the third harmonic. To improve the suppression of the third harmonic, there are three main traditional approaches: First, reduce the distance between the upper and lower layers of metal pillars. However, in high-power systems, to avoid sparks caused by close distances, there is a clear lower limit to the distance adjustment between the metal pillars, which limits the practical effectiveness of this method. Second, increase the number of metal pillar sections. Although this method can improve the filter's harmonic suppression effect to a certain extent, the accompanying problem is that the filter's passband will become narrower, limiting its flexibility in practical applications. The third method is to adjust the narrow side b or wide side a of the input and output waveguide ports (generally, the size of the narrow side b is changed to change the cutoff frequency of the second and third harmonics, thereby improving the depth of harmonic suppression. However, this method is relatively simple in adjusting the bandwidth and harmonic suppression effect, and it is difficult to simultaneously meet the dual requirements of wide passband and high harmonic suppression. While pursuing third harmonic suppression, it often leads to a deterioration in the suppression effect of the second harmonic, and the degree of freedom in structural design is also greatly limited.

[0005] In order to solve the above problem, another idea is to use the method of cascading two low-pass harmonic suppression filters, such as Figure 2 As shown in the figure, the first filter primarily suppresses the second harmonic, while the second focuses on suppressing the third harmonic. By cascading these two filters, dual suppression of the second and third harmonics can be achieved to a certain extent. However, while this approach is effective, it also brings significant challenges. The cascaded design not only increases the overall filter size, creating additional challenges for equipment installation and system integration, but also increases system complexity and cost. Therefore, in practical applications, this approach is not the optimal choice. Summary of the Invention

[0006] This solution aims to overcome at least one defect in the prior art and provide a low-pass harmonic suppression filter to solve the problem that wide passband and high harmonic suppression cannot be achieved simultaneously.

[0007] In order to solve the above technical problems, the following technical solutions are adopted:

[0008] A low-pass harmonic suppression filter, the filter having a plane-symmetrical structure, having a length direction, a width direction, and a height direction perpendicular to each other, and a first symmetry plane perpendicular to the height direction, the structure comprising an input portion, a filter portion, and an output portion sequentially arranged along the length direction; the filter portion comprising six filter cavities, namely a first filter cavity, a second filter cavity, a third filter cavity, a fourth filter cavity, a fifth filter cavity, and a sixth filter cavity sequentially arranged along the length direction, each of which has a first surface and a second surface parallel to each other and symmetrically distributed on both sides of the first symmetry plane; the first surface and second surface of the first filter cavity are provided with a plurality of first metal pillars equidistantly arranged along the width direction, the first surface and second surface of the second filter cavity are provided with a plurality of second metal pillars equidistantly arranged along the width direction, the first surface and second surface of the third filter cavity are provided with a plurality of third metal pillars equidistantly arranged along the width direction, the first surface and second surface of the fourth filter cavity are provided with a plurality of fourth metal pillars equidistantly arranged along the width direction, the first surface and second surface of the fifth filter cavity are provided with a plurality of fifth metal pillars equidistantly arranged along the width direction, and the first surface and second surface of the sixth filter cavity are provided with a plurality of sixth metal pillars equidistantly arranged along the width direction; the height b of the first filter cavity c1 , the height b of the second filter cavity c2 , the height b of the third filter cavity c3 , the height b of the fourth filter cavity c4 , the height b of the fifth filter cavity c5 and the height b of the sixth filter cavity c6 Satisfies: b c1 =b c6 >b c2 =b c5 >b c3 =b c4 , the height b of the first metal column k1 , the height b of the second metal column k2 , the height b of the third metal column k3 , the height b of the fourth metal pillar k4 , the height b of the fifth metal pillar k5 and the height b of the sixth metal pillar k6 Satisfy: (b c1 -2b k1 )=(b c6 -2b k6 )>(b c2 -2b k2 )=(b c5 -2b k5 )>(b c3 -2b k3 )=(b c4 -2b k4 ), the length d of the first metal column k1 , the length of the second metal column dk2 , the length of the third metal column d k3 , the length of the fourth metal column d k4 , the length d of the fifth metal column k5 and the length d of the sixth metal pillar k6 Satisfaction: d k1 =d k6 <d k2 =d k5 <d k3 =d k4 .

[0009] This solution utilizes filter cavities of varying heights and metal pillars of varying sizes (including height and length) to construct a filter structure. This design generates multiple transmission zeros outside the operating frequency band. A transmission zero is a crucial concept in filter design; it indicates a frequency at which the filter's suppression depth is high, meaning that signals have difficulty passing through the filter, thereby suppressing signals at specific frequencies. By carefully designing and adjusting the dimensions of the metal pillars and the height of the filter cavity, this solution creates a continuous sequence of transmission zeros outside the operating frequency band. These transmission zeros not only increase the harmonic suppression width but also provide a steeper roll-off when suppressing harmonics, effectively preventing harmonic signals from passing through. In addition to utilizing transmission zeros to improve harmonic suppression performance, this solution further controls the cutoff frequency of higher-order modes by optimizing the width of the metal pillars. In high-power systems, the generation and transmission of higher-order modes often negatively impacts system performance. By adjusting the width of the metal pillars, this solution precisely adjusts the cutoff frequency of higher-order modes, keeping them away from the operating frequency band, thereby maximizing the transmission of the TE10 mode (the main mode) and reducing unwanted modal interference. Furthermore, by adjusting the size of different filter cavities and the size and spacing of different metal pillars to design the filter structure, a higher degree of design freedom is achieved. This ensures that while meeting the requirements for high harmonic suppression, there is also sufficient distance between the metal pillars to avoid sparks, which is crucial for the stable operation of high-power systems.

[0010] If the passband frequency of the filter is f1~f2, the height b of the first filter cavity is c1 and the height b of the sixth filter cavity c6 Preferably, c / (4*f2)≤b c1 =b c6 ≤c / (4*f1), where c represents the speed of light in vacuum 3*10 8 m / s, in order to obtain a transmission zero point outside the working frequency band and a steeper out-of-band attenuation curve, which is beneficial to further improve the filter's suppression effect on the second harmonic.

[0011] If the passband frequency of the filter is f1~f2, the height b of the second filter cavity isc2 , the height b of the third filter cavity c3 , the height b of the fourth filter cavity c4 and the height b of the fifth filter cavity c5 Preferably, c / (6*f2)≤b c3 =b c4 <b c2 =b c5 ≤c / (6*f1), where c represents the speed of light in vacuum 3*10 8 m / s, in order to obtain the transmission zero point within the third harmonic range and achieve high-frequency harmonic suppression, which is beneficial to further improve the filter's suppression effect on the third harmonic.

[0012] If the passband frequency of the filter is f1~f2, the height b of the first metal column k1 and the length d of the sixth metal pillar k6 Preferably, c / (8*f2)≤d k1 =d k6 ≤c / (8*f1), where c represents the speed of light in vacuum 3*10 8 m / s, in order to obtain a transmission zero point outside the working frequency band and a steeper out-of-band attenuation curve, which is beneficial to further improve the filter's suppression effect on the second harmonic.

[0013] If the passband frequency of the filter is f1~f2, the height b of the second metal column k2 , the height b of the third metal column k3 , the height b of the fourth metal pillar k4 and the height b of the fifth metal pillar k5 Preferably, c / (12*f2)≤b k3 =b k4 <b k2 =b k5 ≤c / (12*f1), where c represents the speed of light in vacuum 3*10 8 m / s, in order to obtain the transmission zero point within the third harmonic range and achieve high-frequency harmonic suppression, which is beneficial to further improve the filter's suppression effect on the third harmonic.

[0014] The length d of the first metal pillar k1 , the length of the second metal column d k2 , the length of the third metal column d k3 , the length of the fourth metal column d k4 , the length d of the fifth metal column k5 and the length d of the sixth metal pillar k6 The initial ratio is: d k1 :d k2 :d k3 :d k4 :dk5 :d k6 =1:2:3:3:2:1, so as to optimize the widths of different metal pillars on this basis to further control the cutoff frequency of the higher-order mode, so that the filter can transmit the TE10 mode as much as possible, which is conducive to further improving the working frequency bandwidth.

[0015] If the passband frequency of the filter is f1~f2, the height b of the input part is p1 and the height b of the output section p2 Preferably meet: b p1 =b p2 ≤c / (6*f2), where c represents the speed of light in vacuum 3*10 8 m / s to ensure complete suppression of the second and third harmonics.

[0016] Input width a p1 and height b p1 , output width a p2 and height b p2 Preferably meet: a p1 =a p2 >b p1 =b p2 .

[0017] The filter preferably has a second symmetry plane perpendicular to the length direction, and the input part and the output part, the first filter cavity and the sixth filter cavity, the second filter cavity and the fifth filter cavity, the third filter cavity and the fourth filter cavity, the first metal column and the sixth metal column, the second metal column and the fifth metal column, and the third metal column and the fourth metal column are all symmetrically arranged on both sides of the second symmetry plane.

[0018] The first surface and the second surface of the first filter cavity can be respectively provided with nine first metal pillars, the first surface and the second surface of the second filter cavity can be respectively provided with nine second metal pillars, the first surface and the second surface of the third filter cavity can be respectively provided with nine third metal pillars, the first surface and the second surface of the fourth filter cavity can be respectively provided with nine fourth metal pillars, the first surface and the second surface of the fifth filter cavity can be respectively provided with nine fifth metal pillars, and the first surface and the second surface of the sixth filter cavity can be respectively provided with nine sixth metal pillars.

[0019] Compared with the existing technology, this solution has the following beneficial effects: This solution uses the height change of the metal column and the height change of the filter cavity in which it is located to generate multiple transmission zeros outside the working frequency band, thereby increasing the harmonic suppression width. On this basis, the length change of the metal column is used to control the cutoff frequency of the high-order mode, so that the filter can transmit the TE10 mode as much as possible. The three work together to achieve a wide working frequency band, high harmonic suppression and a wide harmonic suppression band, effectively avoiding the sparking phenomenon and improving the reliability and stability of the filter in a high-power environment. The realization of these technical effects not only provides new ideas and methods for filter design, but also provides strong technical support for the optimal design of high-power systems, and has important practical value and application prospects.

[0020] In practical applications, this solution's low-pass harmonic suppression filter has demonstrated impressive performance, with a bandwidth exceeding 2.4 GHz. This allows it to support a wider operating frequency band and meet a wider range of application requirements. Furthermore, within the bandwidth, the filter's return loss is better than 20 dB, ensuring minimal energy loss during signal transmission, thereby improving system transmission efficiency. Outside the bandwidth, the filter's suppression capability for second harmonics reaches below -30 dB, and for third harmonics, below -60 dB. This level of suppression is sufficient to effectively prevent harmonic signals from interfering with the system, ensuring stable operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the present invention. To better illustrate the present invention, some components in the accompanying drawings may be omitted, enlarged, or reduced in size, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0022] Figure 1 It is a structural diagram of a traditional low-pass harmonic suppression filter.

[0023] Figure 2 It is a schematic diagram of cascaded low-pass harmonic suppression filters.

[0024] Figure 3 This is a structural diagram of the low-pass harmonic suppression filter of this scheme.

[0025] Figure 4 Schematic diagram of the top view of the low-pass harmonic suppression filter of this scheme.

[0026] Figure 5 This is a side view schematic diagram of the low-pass harmonic suppression filter of this scheme.

[0027] Figure 6 It is the simulated S-parameter curve of the low-pass harmonic suppression filter of this scheme.

[0028] Explanation of the accompanying drawings: input part 100, filtering part 200, first filtering cavity 210, first metal pillar 211, second filtering cavity 220, second metal pillar 221, third filtering cavity 230, third metal pillar 231, fourth filtering cavity 240, fourth metal pillar 241, fifth filtering cavity 250, fifth metal pillar 251, sixth filtering cavity 260, sixth metal pillar 261, output part 300, length direction D, width direction A, height direction B, first symmetry plane 011, second symmetry plane 012, first surface 021, second surface 022. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the present solution, the present solution is further described in detail below with reference to specific embodiments.

[0030] Figures 3-5 This figure shows a possible low-pass harmonic suppression filter with a passband frequency of f1 to f2. It can be applied to high-power systems operating at f1 to f2 to suppress the second and third harmonic signals in the system output frequency range of 2*f1 to 3*f2.

[0031] like Figures 3-5 As shown in FIG, the filter has a length direction D, a width direction A, and a height direction B that are perpendicular to each other, wherein the length direction D is parallel to the transmission direction of the filter. Moreover, the filter is a plane-symmetrical structure, having at least a first symmetry plane 011 perpendicular to the height direction B, i.e., the filter is vertically symmetrical, and even has a second symmetry plane 012 perpendicular to the length direction D, i.e., the filter is bilaterally symmetrical, as shown in FIG. Figure 5 .

[0032] The filter is configured with an input portion 100, a filter portion 200, and an output portion 300, which are sequentially arranged along a length direction D. The input portion 100 has an input port facing away from the filter portion 200, and the output portion 300 has an output port facing away from the filter portion 200. The filter portion 200 is configured with six filter cavities: a first filter cavity 210, a second filter cavity 220, a third filter cavity 230, a fourth filter cavity 240, a fifth filter cavity 250, and a sixth filter cavity 260. The input portion 100, the first filter cavity 210, the second filter cavity 220, the third filter cavity 230, the fourth filter cavity 240, the fifth filter cavity 250, the sixth filter cavity 260, and the output portion 300 are sequentially arranged along a length direction D. They all have a first surface 021 and a second surface 022 that are parallel to each other, and the first surface 021 and the second surface 022 are symmetrically distributed on both sides of the first symmetry plane 011.

[0033] The first surface 021 and the second surface 022 of the first filter cavity 210 are both configured with a plurality of first metal pillars 211 arranged equidistantly along the width direction A, the first surface 021 and the second surface 022 of the second filter cavity 220 are both configured with a plurality of second metal pillars 221 arranged equidistantly along the width direction A, the first surface 021 and the second surface 022 of the third filter cavity 230 are both configured with a plurality of third metal pillars 231 arranged equidistantly along the width direction A, the first surface 021 and the second surface 022 of the fourth filter cavity 240 are both configured with a plurality of fourth metal pillars 241 arranged equidistantly along the width direction A, the first surface 021 and the second surface 022 of the fifth filter cavity 250 are both configured with a plurality of fifth metal pillars 251 arranged equidistantly along the width direction A, and the first surface 021 and the second surface 022 of the sixth filter cavity 260 are both configured with a plurality of sixth metal pillars 261 arranged equidistantly along the width direction A, so that each filter cavity is configured with two layers of metal pillars, and the size and number of the metal pillars in the upper layer are the same as those in the lower layer, so that the filter is symmetrical from top to bottom.

[0034] Specifically, the upper and lower layers of metal pillars of each filter cavity can be set to nine respectively, that is, the first surface 021 and the second surface 022 of the first filter cavity 210 can be respectively configured with nine first metal pillars 211, the first surface 021 and the second surface 022 of the second filter cavity 220 can be respectively configured with nine second metal pillars 221, the first surface 021 and the second surface 022 of the third filter cavity 230 can be respectively configured with nine third metal pillars 231, the first surface 021 and the second surface 022 of the fourth filter cavity 240 can be respectively configured with nine fourth metal pillars 241, the first surface 021 and the second surface 022 of the fifth filter cavity 250 can be respectively configured with nine fifth metal pillars 251, and the first surface 021 and the second surface 022 of the sixth filter cavity 260 can be respectively configured with nine sixth metal pillars 261.

[0035] The input part 100 and the output part 300 are symmetrically arranged on both sides of the second symmetry plane 012, the first filter cavity 210 and its first metal pillar 211 and the sixth filter cavity 260 and its sixth metal pillar 261 are symmetrically arranged on both sides of the second symmetry plane 012, the second filter cavity 220 and its second metal pillar 221 and the fifth filter cavity 250 and its fifth metal pillar 251 are symmetrically arranged on both sides of the second symmetry plane 012, the third filter cavity 230 and its third metal pillar 231 and the fourth filter cavity 240 and its fourth metal pillar 241 are symmetrically arranged on both sides of the second symmetry plane 012, so that the filter is symmetrical on the left and right.

[0036] The height b of the first filter cavity 210 c1 , the height b of the second filter cavity 220 c2 , the height b of the third filter cavity 230 c3 , the height b of the fourth filter cavity 240c4 , the height b of the fifth filter cavity 250 c5 and the height b of the sixth filter cavity 260 c6 Satisfies: b c1 =b c6 >b c2 =b c5 >b c3 =b c4 , that is, the height of the filter cavity gradually decreases from both ends to the middle; the height b of the first metal column 211 k1 , the height b of the second metal pillar 221 k2 , the height b of the third metal pillar 231 k3 , the height b of the fourth metal pillar 241 k4 , the height b of the fifth metal pillar 251 k5 and the height b of the sixth metal pillar 261 k6 Satisfy: (b c1 -2b k1 )=(b c6 -2b k6 )>(b c2 -2b k2 )=(b c5 -2b k5 )>(b c3 -2b k3 )=(b c4 -2b k4 ), that is, the distance between the upper and lower metal pillars gradually decreases from the two ends to the middle; thereby utilizing the height change of the metal pillars and the height change of the filter cavity in which they are located to generate multiple transmission zeros outside the working frequency band to increase the harmonic suppression width. The length d of the first metal pillar 211 k1 , the length d of the second metal pillar 221 k2 , the length d of the third metal pillar 231 k3 , the length d of the fourth metal pillar 241 k4 , the length d of the fifth metal pillar 251 k5 and the length d of the sixth metal pillar 261 k6 Satisfaction: d k1 =d k6 <d k2 =d k5 <d k3 =d k4 The length of the metal pillars increases gradually from the ends to the center. This change in length controls the cutoff frequency of higher-order modes, maximizing the transmission of the TE10 mode by the filter. The synergistic effect of the progressive design of the metal pillar height and length, as well as the progressive design of the height of the filter cavity in which the metal pillars reside, enables a wide operating frequency band, high harmonic suppression, and a wide harmonic suppression band.

[0037] The height b of the first filter cavity 210 c1 and the height b of the sixth filter cavity 260 c6 Satisfies: c / (4*f2)≤b c1 =b c6 ≤c / (4*f1), where c represents the speed of light in vacuum 3*10 8 m / s, thereby obtaining a transmission zero point outside the working frequency band and a steeper out-of-band attenuation curve, which is beneficial to further improve the filter's suppression effect on the second harmonic. c2 , the height b of the third filter cavity 230 c3 , the height b of the fourth filter cavity 240 c4 and the height b of the fifth filter cavity 250 c5 Satisfies: c / (6*f2)≤b c3 =b c4 <b c2 =b c5 ≤c / (6*f1), where c represents the speed of light in vacuum 3*10 8 m / s, thereby obtaining a transmission zero point within the third harmonic range, achieving high-frequency harmonic suppression, and further improving the filter's suppression effect on the third harmonic. When the heights of each filter cavity simultaneously meet the above conditions, it is beneficial to further increase the width of the harmonic suppression band. Figure 3 Taking the structure shown as an example, the three filter cavity heights can generate transmission zeros in the range of 15 to 21 GHz.

[0038] The height b of the first metal pillar 211 k1 and the length d of the sixth metal pillar 261 k6 Satisfies: c / (8*f2)≤d k1 =d k6 ≤c / (8*f1), where c represents the speed of light in vacuum 3*10 8 m / s, thereby obtaining a transmission zero point outside the working frequency band and a steeper out-of-band attenuation curve, which is beneficial to further improve the filter's suppression effect on the second harmonic. k2 , the height b of the third metal pillar 231 k3 , the height b of the fourth metal pillar 241 k4 and the height b of the fifth metal pillar 251 k5 Satisfies: c / (12*f2)≤b k3 =b k4 <b k2 =b k5 ≤c / (12*f1), where c represents the speed of light in vacuum 3*10 8m / s, thereby obtaining a transmission zero point within the third harmonic range, achieving high-frequency harmonic suppression, and further improving the filter's suppression effect on the third harmonic. When the metal column heights of each filter cavity simultaneously meet the above conditions, it is beneficial to further increase the width of the harmonic suppression band. Figure 3 Taking the structure shown as an example, the three metal pillar heights can generate transmission zeros in the range of 13 to 16 GHz.

[0039] The height b of the first filter cavity 210 c1 and the height b of the sixth filter cavity 260 c6 Satisfies: c / (4*f2)≤b c1 =b c6 ≤c / (4*f1), the height b of the second filter cavity 220 c2 , the height b of the third filter cavity 230 c3 , the height b of the fourth filter cavity 240 c4 and the height b of the fifth filter cavity 250 c5 Satisfies: c / (6*f2)≤b c3 =b c4 <b c2 =b c5 ≤c / (6*f1), the height b of the first metal pillar 211 k1 and the length d of the sixth metal pillar 261 k6 Satisfies: c / (8*f2)≤d k1 =d k6 ≤c / (8*f1), and the height b of the second metal pillar 221 k2 , the height b of the third metal pillar 231 k3 , the height b of the fourth metal pillar 241 k4 and the height b of the fifth metal pillar 251 k5 Satisfies: c / (12*f2)≤b k3 =b k4 <b k2 =b k5 When ≤c / (12*f1), it is beneficial to further increase the width of the harmonic suppression band (completely covering the second and third harmonics generated by the working frequency band).

[0040] In high-order mode, TE m0 mode as an example (take m = 1, 2, 3), the formula (f cut_off represents the cutoff frequency, and c represents the speed of light in vacuum (3*10 8 m / s, m ​​and n correspond to the waveguide mode TE respectively mnThe ratio of the cutoff frequencies of the three TE modes is 1:2:3, where m and n (m=1, 2, 3; n=0), a represents the wide side of the input waveguide port, and b represents the narrow side of the output waveguide port) is set to d. k1 , the length d of the second metal pillar 221 k2 , the length d of the third metal pillar 231 k3 , the length d of the fourth metal pillar 241 k4 , the length d of the fifth metal pillar 251 k5 and the length d of the sixth metal pillar 261 k6 The initial ratio is: d k1 :d k2 :d k3 :d k4 :d k5 :d k6 =1:2:3:3:2:1. On this basis, the widths of different metal pillars are optimized to further control the cutoff frequency of the higher-order mode, so that the filter can transmit the TE10 mode as much as possible, which is conducive to further improving the operating bandwidth.

[0041] The width of the input portion 100 and the output portion 300 is generally greater than their height, that is, the width a of the input portion 100 is p1 and height b p1 , the width a of the output portion 300 p2 and height b p2 Satisfaction: a p1 =a p2 >b p1 =b p2 To ensure complete suppression of the second and third harmonics, the height b of the input portion 100 is p1 and the height b of the output portion 300 p2 Satisfies: b p1 =b p2 ≤c / (6*f2), where c represents the speed of light in vacuum 3*10 8 m / s.

[0042] This solution is based on the structure of traditional low-pass harmonic suppression filters. Through a series of ingenious design improvements, it significantly improves the performance of the filter, especially in terms of wide operating frequency band, high harmonic suppression, wide harmonic suppression band and high power adaptability, showing excellent technical results. Traditional low-pass harmonic suppression filters usually achieve basic harmonic suppression functions by arranging metal columns of equal size and equal spacing, but this design often faces problems such as insufficient harmonic suppression depth, limited bandwidth and possible sparking in high-power environments. This solution cleverly breaks through these limitations and achieves a higher degree of design freedom by adjusting the size of different filter cavities and the size and spacing of different metal columns. This ensures that there is sufficient distance between the metal columns to avoid sparking while meeting the high harmonic suppression requirements. This is crucial for the stable operation of high-power systems.

[0043] Specifically, this solution utilizes filter cavities of different heights and metal pillars of different sizes (including height and length) to construct a filter structure. Not only do the heights and lengths of the different metal pillars differ, but the heights of the filter cavities in which the different metal pillars are located are also different. This design can generate multiple transmission zeros outside the operating frequency band. Transmission zero is an important concept in filter design. It means that at this frequency point, the suppression depth of the filter is high, that is, it is difficult for the signal to pass through the filter, thereby achieving suppression of specific frequency signals. By carefully designing and adjusting the size of the metal pillars and the height of the filter cavity, this solution can form a continuous sequence of transmission zeros outside the operating frequency band. These transmission zeros not only increase the width of harmonic suppression, but also make the filter have a steeper roll-off characteristic when suppressing harmonics, thereby more effectively preventing the passage of harmonic signals.

[0044] In addition to utilizing transmission zeros to improve harmonic suppression, this solution further controls the cutoff frequency of higher-order modes by optimizing the width of different metal pillars. In high-power systems, the generation and transmission of higher-order modes often adversely impact system performance. By adjusting the width of the metal pillars, this solution precisely adjusts the cutoff frequency of higher-order modes, keeping them out of the operating frequency band. This maximizes the transmission of the TE10 mode (the main mode) and reduces unnecessary modal interference.

[0045] In practical applications, the low-pass harmonic suppression filter of this solution has shown impressive performance indicators, such as Figure 6As shown, its bandwidth exceeds 2.4 GHz, which means it can support a wider operating frequency band and meet more diverse application requirements. Furthermore, within the bandwidth, the filter's return loss is better than 20 dB, ensuring that energy loss during signal transmission is kept to a minimum, thereby improving system transmission efficiency. Outside the bandwidth, the filter's suppression capability for second harmonics reaches below -30 dB, and for third harmonics, below -60 dB. This suppression depth is sufficient to effectively prevent harmonic signals from interfering with the system and ensure stable operation.

[0046] In summary, this low-pass harmonic suppression filter achieves multiple technological breakthroughs through innovative structural design and optimization strategies, including high-harmonic suppression, wide harmonic suppression band, and high-power adaptability. It not only addresses the shortcomings of traditional filters in harmonic suppression and bandwidth, but also effectively prevents sparking by optimizing the size and spacing of metal pillars, improving the filter's reliability and stability in high-power environments. The achievement of these technical results not only provides new ideas and methods for filter design, but also provides strong technical support for the optimized design of high-power systems, possessing significant practical value and application prospects.

[0047] Obviously, the above embodiments of this solution are merely examples for the purpose of clarifying this solution and are not intended to limit the implementation of this solution. Those skilled in the art will be able to make other variations or modifications based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this solution shall be included within the scope of protection of the claims of this solution.

Claims

1. A low-pass harmonic suppression filter, characterized in that: The filter is a plane-symmetrical structure having a length direction, a width direction and a height direction perpendicular to each other, and a first symmetry plane perpendicular to the height direction. Its structure includes an input part, a filtering part and an output part arranged in sequence along the length direction; the filtering part includes six filter cavities, namely a first filter cavity, a second filter cavity, a third filter cavity, a fourth filter cavity, a fifth filter cavity and a sixth filter cavity arranged in sequence along the length direction, all of which have a first surface and a second surface parallel to each other and symmetrically distributed on both sides of the first symmetry plane; the first surface and the second surface of the first filter cavity are provided with a plurality of first metal pillars arranged equidistantly along the width direction, the first surface and the second surface of the second filter cavity are provided with a plurality of second metal pillars arranged equidistantly along the width direction, the first surface and the second surface of the third filter cavity are provided with a plurality of third metal pillars arranged equidistantly along the width direction, the first surface and the second surface of the fourth filter cavity are provided with a plurality of fourth metal pillars arranged equidistantly along the width direction, the first surface and the second surface of the fifth filter cavity are provided with a plurality of fifth metal pillars arranged equidistantly along the width direction, and the first surface and the second surface of the sixth filter cavity are provided with a plurality of sixth metal pillars arranged equidistantly along the width direction; The height b of the first filter cavity c1 , the height b of the second filter cavity c2 , the height b of the third filter cavity c3 , the height b of the fourth filter cavity c4 , the height b of the fifth filter cavity c5 and the height b of the sixth filter cavity c6 Satisfies: b c1 =b c6 >b c2 =b c5 >b c3 =b c4 , the height b of the first metal column k1 , the height b of the second metal column k2 , the height b of the third metal column k3 , the height b of the fourth metal column k4 , the height b of the fifth metal column k5 and the height b of the sixth metal pillar k6 Satisfy: (b c1 -2b k1 )=(b c6 -2b k6 )>(b c2 -2b k2 )=(b c5 -2b k5 )>(b c3 -2b k3 )=(b c4 -2b k4 ), the length d of the first metal column k1 , the length d of the second metal column k2 , the length d of the third metal column k3 , the length d of the fourth metal column k4 , the length d of the fifth metal column k5 and the length d of the sixth metal pillar k6 Satisfaction: d k1 =d k6 <d k2 =d k5 <d k3 =d k4 .

2. The low-pass harmonic suppression filter according to claim 1, characterized in that: The passband frequency of the filter is f1-f2, and the height b of the first filter cavity is c1 and the height b of the sixth filter cavity c6 Satisfies: c / (4*f2)≤b c1 =b c6 ≤c / (4*f1), where c represents the speed of light in vacuum 3*10 8 m / s.

3. The low-pass harmonic suppression filter according to claim 1, characterized in that: The passband frequency of the filter is f1-f2, and the height b of the second filter cavity is c2 , the height b of the third filter cavity c3 , the height b of the fourth filter cavity c4 and the height b of the fifth filter cavity c5 Satisfies: c / (6*f2)≤b c3 =b c4 <b c2 =b c5 ≤c / (6*f1), where c represents the speed of light in vacuum 3*10 8 m / s.

4. The low-pass harmonic suppression filter according to any one of claims 1 to 3, characterized in that: The passband frequency of the filter is f1-f2, and the height b of the first metal column is k1 and the length d of the sixth metal pillar k6 Satisfies: c / (8*f2)≤d k1 =d k6 ≤c / (8*f1), where c represents the speed of light in vacuum 3*10 8 m / s.

5. The low-pass harmonic suppression filter according to any one of claims 1 to 3, characterized in that: The passband frequency of the filter is f1-f2, and the height b of the second metal column is k2 , the height b of the third metal column k3 , the height b of the fourth metal column k4 and the height b of the fifth metal pillar k5 Satisfies: c / (12*f2)≤b k3 =b k4 <b k2 =b k5 ≤c / (12*f1), where c represents the speed of light in vacuum 3*10 8 m / s.

6. The low-pass harmonic suppression filter according to any one of claims 1 to 3, characterized in that: The length d of the first metal column k1 , the length d of the second metal column k2 , the length d of the third metal column k3 , the length d of the fourth metal column k4 , the length d of the fifth metal column k5 and the length d of the sixth metal pillar k6 The initial ratio is: d k1 :d k2 :d k3 :d k4 :d k5 :d k6 =1:2:3:3:2:

1.

7. The low-pass harmonic suppression filter according to any one of claims 1 to 3, characterized in that: The passband frequency of the filter is f1-f2, and the height b of the input portion is p1 and the height b of the output portion p2 Satisfies: b p1 =b p2 ≤c / (6*f2), where c represents the speed of light in vacuum 3*10 8 m / s.

8. The low-pass harmonic suppression filter according to any one of claims 1 to 3, characterized in that: The width a of the input portion p1 and height b p1 , the width a of the output portion p2 and height b p2 Satisfaction: a p1 =a p2 >b p1 =b p2 .

9. The low-pass harmonic suppression filter according to any one of claims 1 to 3, characterized in that: The filter also has a second symmetry plane perpendicular to the length direction, and the input part and the output part, the first filter cavity and the sixth filter cavity, the second filter cavity and the fifth filter cavity, the third filter cavity and the fourth filter cavity, the first metal column and the sixth metal column, the second metal column and the fifth metal column, and the third metal column and the fourth metal column are all symmetrically arranged on both sides of the second symmetry plane.

10. The low-pass harmonic suppression filter according to any one of claims 1 to 3, characterized in that: The first surface and the second surface of the first filter cavity are respectively provided with nine first metal pillars, the first surface and the second surface of the second filter cavity are respectively provided with nine second metal pillars, the first surface and the second surface of the third filter cavity are respectively provided with nine third metal pillars, the first surface and the second surface of the fourth filter cavity are respectively provided with nine fourth metal pillars, the first surface and the second surface of the fifth filter cavity are respectively provided with nine fifth metal pillars, and the first surface and the second surface of the sixth filter cavity are respectively provided with nine sixth metal pillars.

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