Low-pass harmonic suppression filter

Abstract

The low-pass harmonic suppression filter is provided with six filter cavities, the upper surface and the lower surface of each filter cavity are each provided with a plurality of metal columns arranged at equal intervals, and the height bc1 of the first filter cavity, the height bc2 of the second filter cavity, the height bc3 of the third filter cavity, the height bc4 of the fourth filter cavity, the height bc5 of the fifth filter cavity and the height bc6 of the sixth filter cavity meet the formula that bc1 = bc6 > bc2 = bc5 > bc3 = bc4, the height bk1 of the first metal column, the height bk2 of the second metal column, the height bk3 of the third metal column, the height bk4 of the fourth metal column, the height bk5 of the fifth metal column and the height bk6 of the sixth metal column meet the following conditions: (bc1-2bk1) = (bc6-2bk6) > (bc2-2bk2) = (bc5-2bk5) > (bc3-2bk3) = (bc4-2bk4), the length dk1 of the first metal column, the length dk2 of the second metal column, the length dk3 of the third metal column, the length dk4 of the fourth metal column, the length dk5 of the fifth metal column and the length dk6 of the sixth metal column meet the following condition: dk1 = dk6 < dk2 = dk5 < dk3 = dk4, so that the filter can simultaneously realize wide working frequency band, high harmonic suppression and wide harmonic suppression band.

Description

Technical Field

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

[0002] In the design and operation of high-power systems, the signal characteristics of the system output are crucial considerations. High-power signals not only carry the operating frequency band information required by the system, but are also often accompanied by a series of high-power harmonic signals. Although these harmonic signals, such as secondary and tertiary modes, are not directly required by the system, their powerful output power may pose a potential threat to the normal operation of the system. In order to ensure the stability and reliability of system performance, effective measures must be taken to filter out these harmonic signals. As the main undertaker of this task, the importance of harmonic suppression filters is self-evident.

[0003] The working principle of the harmonic suppression filter is that it can identify and filter out the non-working frequency band components in the signal, that is, those high-power harmonic signals. In practical applications, there are various types and structures of filters to meet the needs of different systems. Among them, microstrip harmonic suppression filters and waveguide harmonic suppression filters are two more common types. Microstrip filters have been widely used in some occasions due to their small size and simple processing. However, for high-power systems, the power capacity of microstrip lines is limited, and the transmission loss is relatively large, which limits its application potential in high-power environments. In contrast, although the waveguide harmonic suppression filter is slightly larger in size, its low transmission loss and high power capacity make it an ideal choice for high-power systems. By placing the waveguide harmonic suppression filter at the final stage of the system output, it can not only ensure that the signals in the working frequency band can be output to the maximum extent, but also effectively suppress those high-power second and third harmonic signals, thereby ensuring the stable operation of the system.

[0004] However, even waveguide harmonic suppression filters face many challenges in design and application. The traditional low-pass harmonic suppression filter structure is as follows: Figure 1As shown in the figure, metal columns of the same size are arranged equidistantly to achieve the effect of harmonic suppression. Although the effect of harmonic suppression can be achieved to a certain extent, it is often incapable of suppressing the third harmonic. In order to improve the suppression effect of the third harmonic, there are three main ideas in the traditional method: one is to reduce the distance between the upper and lower layers of metal columns. However, in high-power systems, in order to avoid sparking caused by too close distance, there is a clear lower limit for adjusting the distance between metal columns, which limits the actual effect of this method. The second is to increase the number of metal columns. Although this method can improve the harmonic suppression effect of the filter to a certain extent, the problem that comes with it is that the passband of the filter will become narrower, thereby 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, so as to improve the depth of harmonic suppression. However, this method is relatively simple in adjusting the bandwidth and harmonic suppression effect, and it is difficult to meet the dual needs of wide passband and high harmonic suppression at the same time. While pursuing the suppression of the third harmonic, it often leads to a deterioration in the suppression effect of the second harmonic, and the freedom of structural design is also greatly limited.

[0005] To solve the above problems, another approach is to cascade two low-pass harmonic suppression filters, such as Figure 2 As shown in the figure. The first filter is mainly used to suppress the second harmonic, while the second one 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, although this method is effective, the problems it brings cannot be ignored. The cascade design not only increases the overall size of the filter, brings additional challenges to equipment installation and system integration, but also increases the complexity and cost of the system. Therefore, in practical applications, this method is not the best choice. Summary of the invention

[0006] The present invention 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 is a plane-symmetrical structure, has 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 of which includes an input part, a filter part and an output part arranged in sequence along the length direction; the filter part includes six filter cavities, which are respectively 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, and they all have a first surface and a second surface which are 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 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 of the fifth metal column d 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 scheme uses filter cavities of different heights and metal pillars of different sizes (including height and length) to construct the filter structure. This design can generate multiple transmission zeros outside the working 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 pillar and the height of the filter cavity, this scheme can form a continuous sequence of transmission zeros outside the working 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. In addition to using transmission zeros to improve harmonic suppression performance, this scheme also 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 have an adverse effect on the performance of the system. By adjusting the width of the metal pillar, this scheme can accurately adjust the cutoff frequency of the higher-order mode to keep it away from the working frequency band, thereby transmitting the TE10 mode (i.e., the main mode) as much as possible and reducing unnecessary mode interference. Moreover, by adjusting the size of different filter cavities and the size and spacing of different metal pillars to design the structure of the filter, a higher degree of design freedom is achieved, thereby meeting the requirements of high harmonic suppression while ensuring that there is enough 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 f 1 ~f 2 , then the height b of the first filter cavity c1 and the height b of the sixth filter cavity c6 The best solution is: c / (4*f 2 )≤b c1 =b c6 ≤c / (4*f 1 ), 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 f 1 ~f 2 , then 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 and the height b of the fifth filter cavity c5 The best solution is: c / (6*f 2 )≤b c3 =b c4 <b c2 =b c5 ≤c / (6*f 1 ), 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 f 1 ~f 2 , the height b of the first metal column k1 and the length d of the sixth metal pillar k6 The best solution is: c / (8*f 2 )≤d k1 =d k6 ≤c / (8*f 1 ), 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 f 1 ~f 2 , 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 The best solution is: c / (12*f 2 )≤b k3 =b k4 <b k2 =b k5 ≤c / (12*f 1 ), 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 column 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 of the fifth metal column d 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, so that on this basis the widths of different metal pillars can be 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 working frequency bandwidth.

[0015] If the passband frequency of the filter is f 1 ~f 2 , then the height of the input part b p1 and the height b of the output section p2 Preferably meet: b p1 =b p2 ≤c / (6*f 2 ), 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, 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 prior art, this solution has the following beneficial effects: This solution utilizes 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 operating 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, the low-pass harmonic suppression filter of this solution has shown impressive performance indicators, and its bandwidth has reached more than 2.4GHz, which means that it can support a wider operating frequency band and meet more diverse application requirements. At the same time, within the bandwidth, the return loss of the filter is better than 20dB, which ensures that the energy loss of the signal during transmission is controlled at a low level, thereby improving the transmission efficiency of the system. Outside the bandwidth, the filter's suppression ability for the second harmonic reaches below -30dB, and the suppression of the third harmonic reaches below -60dB. Such a suppression depth is sufficient to effectively prevent harmonic signals from interfering with the system and ensure the stable operation of the system. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

[0026] Figure 5 It 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 filter cavity 210, first metal pillar 211, second filter cavity 220, second metal pillar 221, third filter cavity 230, third metal pillar 231, fourth filter cavity 240, fourth metal pillar 241, fifth filter cavity 250, fifth metal pillar 251, sixth filter 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 in conjunction with specific embodiments.

[0030] Figures 3 to 5 A possible low-pass harmonic suppression filter is shown. The passband frequency of this filter is f 1 ~f 2 , can be applied to the working frequency f 1 ~f 2 The high power system can suppress the frequency range of the system output to 2*f 1 ~3*f 2 The second and third harmonic signals.

[0031] like Figures 3 to 5 As shown in FIG. 1 , 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 provided with an input part 100, a filter part 200 and an output part 300, and the input part 100, the filter part 200 and the output part 300 are sequentially arranged along the length direction D. The input part 100 has an input port facing away from the filter part 200, the output part 300 has an output port facing away from the filter part 200, and the filter part 200 is provided with six filter cavities, namely, 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 part 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 part 300 are sequentially arranged along the length direction D, and they all have a first surface 021 and a second surface 022 which 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 upper and lower layers of metal pillars, and the size and quantity of the metal pillars of the upper layer are the same as those of the metal pillars of 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 column 211 and the sixth filter cavity 260 and its sixth metal column 261 are symmetrically arranged on both sides of the second symmetry plane 012, the second filter cavity 220 and its second metal column 221 and the fifth filter cavity 250 and its fifth metal column 251 are symmetrically arranged on both sides of the second symmetry plane 012, the third filter cavity 230 and its third metal column 231 and the fourth filter cavity 240 and its fourth metal column 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 240 c4 , 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 231k3 , 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 , that is, the length of the metal column increases gradually from both ends to the middle, and the change in the length 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 progressive design of the height and length of the metal column and the progressive design of the height of the filter cavity where the metal column is located work together to achieve 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*f 2 )≤b c1 =b c6 ≤c / (4*f 1 ), 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*f 2 )≤b c3 =b c4 <b c2 =b c5 ≤c / (6*f 1 ), where c represents the speed of light in vacuum 3*10 8 m / s, thereby obtaining the 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 meet the above conditions at the same time, 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 k6Satisfies: c / (8*f 2 )≤d k1 =d k6 ≤c / (8*f 1 ), 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*f 2 )≤b k3 =b k4 <b k2 =b k5 ≤c / (12*f 1 ), where c represents the speed of light in vacuum 3*10 8 m / s, thereby obtaining the 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 meet the above conditions at the same time, 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*f 2 )≤b c1 =b c6 ≤c / (4*f 1 ), 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*f 2 )≤b c3 =b c4 <b c2 =b c5 ≤c / (6*f 1 ), the height b of the first metal pillar 211 k1 and the length d of the sixth metal pillar 261 k6 Satisfies: c / (8*f 2 )≤d k1 =dk6 ≤c / (8*f 1 ), 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*f 2 )≤b k3 =b k4 <b k2 =b k5 ≤c / (12*f 1 ), it is beneficial to further increase the width of the harmonic suppression band (completely covering the second and third harmonics generated in the working frequency band).

[0040] In high-order mode, TE m0 mode as an example (take m = 1, 2, 3), according to the formula (f cut_off represents the cut-off frequency, c represents the speed of light in vacuum 3*10 8 m / s, m ​​and n correspond to the waveguide mode TE respectively mn m and n in (take m = 1, 2, 3; n = 0, a represents the wide side of the input waveguide port, b represents the narrow side of the output waveguide port) the ratio of the cutoff frequencies of the three TE modes is 1:2:3, thus setting the length d of the first metal column 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 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 working frequency bandwidth.

[0041] The width of the input portion 100 and the output portion 300 is usually greater than its 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 Satisfy: 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*f 2 ), where c represents the speed of light in vacuum 3*10 8 m / s.

[0042] This scheme is based on the structure of the traditional low-pass harmonic suppression filter. Through a series of clever design improvements, the performance of the filter has been significantly improved, especially in terms of wide operating frequency band, high harmonic suppression, wide harmonic suppression band and high power adaptability, showing excellent technical effects. 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 scheme 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. While meeting the requirements of high harmonic suppression, it also ensures that there is enough distance between metal columns to avoid sparking, which is crucial for the stable operation of high-power systems.

[0043] Specifically, this scheme uses filter cavities of different heights and metal pillars of different sizes (including height and length) to construct a filter structure. Not only are the heights and lengths of different metal pillars different, but the heights of the filter cavities where different metal pillars are located are also different. This design can generate multiple transmission zeros outside the working 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 scheme can form a continuous sequence of transmission zeros outside the working 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 using transmission zeros to improve harmonic suppression performance, this solution further controls the cutoff frequency of higher-order modes by optimizing the width of different metal columns. In high-power systems, the generation and transmission of higher-order modes often have an adverse effect on system performance. By adjusting the width of the metal column, this solution can accurately adjust the cutoff frequency of the higher-order mode to keep it away from the working frequency band, thereby transmitting the TE10 mode (i.e., the main mode) as much as possible and reducing unnecessary mode interference.

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

[0046] In summary, the low-pass harmonic suppression filter of this scheme has achieved technical breakthroughs in high harmonic suppression, high harmonic suppression, wide harmonic suppression band and high power adaptability through innovative structural design and optimization strategies. It not only solves the shortcomings of traditional filters in harmonic suppression and bandwidth, but also effectively avoids sparking by optimizing the size and spacing of metal columns, and improves the reliability and stability of the filter in high-power environments. The realization of these technical effects not only provides new ideas and methods for filter design, but also provides strong technical support for the optimization design of high-power systems, which has important practical value and application prospects.

[0047] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation methods here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the claims of the present invention.

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, and its structure includes an input part, a filter part and an output part arranged in sequence along the length direction; the filter 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, and they all 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 pillar 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 Satisfy: 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, 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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