Improved waveguide filter and manufacturing method thereof

Abstract

The invention discloses an improved waveguide filter, and relates to the technical field of filters, the improved waveguide filter comprises a waveguide filter main body and a waveguide cavity arranged in the waveguide filter main body, and the interior of the waveguide cavity is divided into a plurality of traditional waveguide resonant cavities. At least one traditional waveguide resonant cavity forms a single-ridge waveguide resonant cavity through a single-ridge waveguide resonator and is used for introducing a transmission zero point at the high end of the amplitude-frequency characteristic of the filter and improving the steepness of the amplitude-frequency characteristic of the high end. According to the improved waveguide filter, a transmission zero point is naturally introduced to a high end through the single-ridge resonant cavity, and a complex coupling structure is not needed; the amplitude-frequency characteristic symmetry is remarkably improved, and the high-end steepness is effectively improved; the insertion loss is basically unchanged, and even is slightly reduced due to structure optimization; the design is flexible, and the zero frequency and depth can be controlled by adjusting single ridge parameters; the technology is compatible with a traditional waveguide, and mass production and popularization are facilitated.

Description

Technical Field

[0001] This invention relates to the field of filter technology, specifically to an improved waveguide filter and its fabrication method. Background Technology

[0002] Traditional waveguide filters are widely used in microwave systems due to their advantages such as simple structure, high power capacity, and low insertion loss. A typical waveguide filter uses a series half-wavelength resonant cavity, with inter-cavity coupling achieved through an inductive diaphragm. However, these filters generally suffer from asymmetric amplitude-frequency characteristics in broadband designs: steep attenuation in the low-frequency band and gentle attenuation in the high-frequency band, resulting in insufficient high-side rejection.

[0003] To improve high-end performance, the traditional approach is to increase the filter order, but this introduces additional losses, increases size and cost; even if transmission zeros are introduced through cross-coupling or non-adjacent cavity coupling, the structure is often complex, difficult to debug, and prone to sacrificing in-band performance. Summary of the Invention

[0004] The purpose of this invention is to provide an improved waveguide filter and its manufacturing method to overcome the shortcomings of the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an improved waveguide filter, comprising a waveguide filter body and a waveguide cavity formed within the waveguide filter body, wherein the waveguide cavity is divided into multiple conventional waveguide resonant cavities, and at least one conventional waveguide resonant cavity is constructed into a single-ridge waveguide resonant cavity by means of a single-ridge waveguide resonator, and is used to introduce a transmission zero at the high end of the filter's amplitude-frequency characteristics to improve the steepness of the high end amplitude-frequency characteristics.

[0006] Preferably, the single-ridge waveguide resonator of the single-ridge waveguide resonator is used to replace at least one half-wavelength waveguide cavity resonator in a conventional waveguide filter.

[0007] Preferably, the waveguide filter body further includes an inductive diaphragm for forming a parallel inductive coupling structure between resonant cavities.

[0008] 4. A method for manufacturing an improved waveguide filter, comprising the following steps: S1, based on the center frequency of the filter... ,bandwidth Based on out-of-band suppression requirements, the filter order n and the number of resonant cavities are determined; at least one traditional waveguide resonant cavity is selected and a single-ridge waveguide resonator is used, while the remaining resonant cavities are traditional rectangular waveguide cavities; a filter model is established using three-dimensional electromagnetic simulation software, and the ridge height of the single ridge is determined. ridge width Length of the spine and its longitudinal position within the cavity Perform parametric scanning; optimize the single-ridge resonator to achieve the target high-end frequencies. S1. Introducing a transmission zero point and ensuring in-band matching and low loss; S2. Selecting a high-conductivity metal material to process the waveguide cavity, using CNC milling technology for one-time forming; The single-ridge structure is milled integrally with the cavity or vacuum brazed after separate processing to ensure continuous electrical contact; The inner wall of the cavity undergoes surface treatment, including polishing, silver plating, or gold plating, to reduce surface roughness and loss; S3. The inductor diaphragm uses the same material as the cavity, fabricated through wire cutting or photolithography, with the diaphragm opening shape being rectangular or circular; The diaphragm thickness... and opening size Precise control is achieved based on the coupling coefficient determined by simulation; the diaphragm is installed in the partition groove between the resonant cavities, and fixed by conductive adhesive or laser welding; S4, tuning screws are installed at the center position of each resonant cavity, and the screw material is selected as non-magnetic metal; real-time monitoring is combined with a vector network analyzer. and Parameters; adjust the depth of each screw sequentially, prioritizing optimization of the center frequency and bandwidth, and then finely adjust the high-end transmission zero position; S5, test the full-band S-parameters of the filter to verify in-band insertion loss, out-of-band rejection, and high-end steepness; perform temperature cycling and vibration tests to verify the filter's performance stability under environmental stress; perform helium mass spectrometry leak testing on qualified products to ensure that the airtightness meets the requirements of high-reliability applications. Preferably, the ridge height of the single-ridge waveguide resonator in step S1 is... satisfy:

[0009] in, This represents the height of the waveguide cavity.

[0010] Preferably, the opening area of ​​the inductor diaphragm in step S3 is... satisfy: in, Waveguide wavelength is the characteristic impedance, and k is the coupling coefficient, with a value ranging from 0.05 to 0.3.

[0011] Preferably, the tuning accuracy of the tuning screw in step S4 is not less than 0.01. Furthermore, an iterative optimization algorithm is used to automate the tuning process.

[0012] In the above technical solution, the present invention provides an improved waveguide filter and its manufacturing method, which naturally introduces a transmission zero at the high end through a single-ridge resonant cavity without the need for a complex coupling structure; the amplitude-frequency characteristic symmetry is significantly improved, effectively increasing the high-end steepness; the insertion loss remains basically unchanged, and may even be slightly reduced due to structural optimization; the design is flexible, and the zero frequency and depth can be controlled by adjusting the single-ridge parameters; the process is compatible with traditional waveguides, facilitating mass production and promotion. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0014] Figure 1 This is a schematic diagram of a waveguide filter structure provided in an embodiment of the present invention; Figure 2 A comparison diagram of the amplitude-frequency response curves of a conventional waveguide filter and an improved waveguide filter provided in an embodiment of the present invention; Figure 3 This is a process flow diagram of the method for manufacturing the main body of the wave-matching filter provided in an embodiment of the present invention.

[0015] Explanation of reference numerals in the attached figures: 1. Waveguide filter body; 2. Waveguide cavity; 3. Traditional waveguide resonant cavity; 4. Single-ridge waveguide resonant cavity; 5. Inductor diaphragm; 6. Single-ridge waveguide resonator. Detailed Implementation

[0016] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0017] Please see Figure 1-3 An improved waveguide filter provided in this embodiment of the invention includes a waveguide filter body 1 and a waveguide cavity 2 formed within the waveguide filter body 1. The waveguide cavity 2 is divided into multiple conventional waveguide resonant cavities 3. At least one conventional waveguide resonant cavity 3 is constructed into a single-ridge waveguide resonant cavity 4 by a single-ridge waveguide resonator 6, and is used to introduce a transmission zero at the high end of the filter's amplitude-frequency characteristics to improve the steepness of the high end amplitude-frequency characteristics.

[0018] Among them, the single-ridge waveguide resonator 6 of the single-ridge waveguide resonator 4 is used to replace at least one half-wavelength waveguide cavity resonator in a conventional waveguide filter.

[0019] The waveguide filter body 1 also includes an inductor diaphragm 5, which is used to form a parallel inductor coupling structure between resonant cavities.

[0020] An improved waveguide filter fabrication method includes the following steps: S1, based on the center frequency of the filter... ,bandwidth Based on out-of-band suppression requirements, the filter order n and the number of resonant cavities are determined; at least one conventional waveguide resonant cavity 3 is selected and a single-ridge waveguide resonator 6 is used, while the remaining resonant cavities are conventional rectangular waveguide cavities; a filter model is established using three-dimensional electromagnetic simulation software, and the ridge height of the single ridge is determined. ridge width ridge length and the longitudinal position of the spine in the cavity Perform parametric scanning; optimize the single-ridge resonator to achieve the target high-end frequencies. The process involves introducing a transmission zero and ensuring in-band matching and low loss. Specifically, this process is an electrical design and simulation optimization step, which can be achieved using HFSS software for modeling and parameter scanning to optimize ridge height, ridge width, and diaphragm opening. In a practical embodiment, simulation results show that the ridge width is much smaller than the ridge height, and the ridge width is comparable to the width of the inductor diaphragm. Specifically, with a ridge height of 3.6 mm, a ridge width of 1.0 mm, a ridge length of 7.5 mm, and a ridge rotation angle of 20°, a transmission zero with a depth exceeding -100 dB can be formed at 22.5 GHz.

[0021] S2. The waveguide cavity 2 is fabricated from a high-conductivity metal material and formed in one step using CNC milling. The single-ridge structure is either integrally milled with the cavity or machined separately and then vacuum brazed to ensure continuous electrical contact. The inner wall of the cavity undergoes surface treatment, including polishing, silver plating, or gold plating, to reduce surface roughness and loss. Specifically, this process involves precision machining of the cavity, which can be achieved using a five-axis CNC milling machine to produce the cavity structure with a single ridge in one step, with a positioning accuracy of ±0.01 mm. The single ridge and the cavity are an integrated design and require no assembly.

[0022] S3, the inductor diaphragm 5 is made of the same material as the cavity and is fabricated by wire cutting or photolithography. The diaphragm opening shape is rectangular or circular; the diaphragm thickness... and opening size Precise control is achieved based on the coupling coefficient determined by simulation; the diaphragm is installed in the partition groove between the resonant cavities and fixed by conductive adhesive or laser welding; this process also requires surface treatment. In the preferred embodiment, the inner wall of the cavity is mechanically polished to Ra ≤ 0.4 μm, followed by chemical silver plating with a plating thickness of 4 to 6 μm.

[0023] S4. Install tuning screws at the center of each resonant cavity. The screws should be made of a non-magnetic, adjustable metal. Monitor the tuning screws in real time using a vector network analyzer. and Parameters: Adjust the depth of each screw sequentially, prioritizing optimization of the center frequency and bandwidth, and then finely adjust the high-side transmission zero position; after installing the tuning screws, connect the vector network analyzer and the automated tuning software. Use an iterative algorithm to adjust the depth of each screw sequentially, prioritizing optimization of passband matching, and then finely adjust the transmission zero position.

[0024] S5. Test the full-band S-parameters of the filter (which can be tested in natural environments, preferably in a microwave anechoic chamber) to verify in-band insertion loss, out-of-band rejection, and high-end steepness; conduct temperature cycling and vibration tests to verify the performance stability of the filter under environmental stress; perform helium mass spectrometry leak detection on qualified products to ensure that the airtightness meets the requirements of high reliability applications.

[0025] In step S1, the ridge height of the single-ridge waveguide resonant cavity 4 satisfy: in, Waveguide wavelength Let be the characteristic impedance, and k be the coupling coefficient, ranging from 0.05 to 0.3. In step S4, the tuning accuracy of the tuning screw should not be less than 0.01. Furthermore, an iterative optimization algorithm is used to automate the tuning process.

[0026] In a specific embodiment, the waveguide filter body 1 employs a 7-cavity structure, wherein the fourth cavity is preferably a single-ridge waveguide resonant cavity 4; and the cavity material is preferably an aluminum-magnesium alloy (AlMg3). Furthermore, the height of the single ridge can be dynamically adjusted via a micro-actuator, enabling the transmission zero-point frequency to be adjustable within a range of ±5%. This is suitable for cognitive radio and frequency agile systems. Simultaneously, the ridge is designed in sections, using piezoelectric ceramic actuators to change the distance between the ridge and the top wall; the control system dynamically adjusts the zero-point position according to the communication protocol; and machine learning algorithms are used to optimize the tuning trajectory during the debugging process.

[0027] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. An improved waveguide filter, comprising a waveguide filter body and a waveguide cavity formed within the waveguide filter body, wherein the waveguide cavity is divided into multiple conventional waveguide resonant cavities, characterized in that: At least one conventional waveguide resonator is constructed into a single-ridge waveguide resonator through a single-ridge waveguide resonator, and is used to introduce a transmission zero at the high end of the amplitude-frequency characteristic of the filter, thereby improving the steepness of the high end amplitude-frequency characteristic.

2. An improved waveguide filter according to claim 1, characterized in that, A single-ridge waveguide resonator is used to replace at least one half-wavelength waveguide cavity resonator in a conventional waveguide filter.

3. An improved waveguide filter according to claim 1, characterized in that, The waveguide filter body also includes an inductor diaphragm for forming a parallel inductive coupling structure between resonant cavities.

4. A method for fabricating any of the improved waveguide filters described in claims 1-3, characterized in that, Includes the following steps S1. Based on the center frequency of the filter , Based on out-of-band suppression requirements, the filter order n and the number of resonant cavities are determined; at least one traditional waveguide resonant cavity is selected and a single-ridge waveguide resonator is used, while the remaining resonant cavities are traditional rectangular waveguide cavities; a filter model is established using three-dimensional electromagnetic simulation software, and the ridge height of the single ridge is determined. ridge width ridge length and the longitudinal position of the spine in the cavity Perform parametric scanning; optimize the single-ridge resonator to achieve the target high-end frequencies. A transmission zero is introduced at the point of intersection, and in-band matching and low loss are ensured; S2. The waveguide cavity is made of a metal material with high conductivity and formed in one step by CNC milling. The single ridge structure is milled as an integral part of the cavity or vacuum brazed after separate processing to ensure continuous electrical contact. The inner wall of the cavity is surface treated, including polishing, silver plating or gold plating, to reduce surface roughness and loss. S3. The inductor diaphragm is made of the same material as the cavity and is fabricated using wire cutting or photolithography. The diaphragm opening shape is rectangular or circular; the diaphragm thickness... and opening size Precise control is performed based on the coupling coefficient determined by simulation; the diaphragm is installed in the partition groove between the resonant cavities and fixed by conductive adhesive or laser welding; precise control is performed based on the coupling coefficient determined by simulation; the diaphragm is installed in the partition groove between the resonant cavities and fixed by conductive adhesive or laser welding. S4. Install tuning screws at the center of each resonant cavity; the screws should be made of non-magnetic metal. Monitor in real-time using a vector network analyzer. and Parameters; adjust the depth of each screw in sequence, prioritize optimizing the center frequency and bandwidth, and then finely adjust the high-end transmission zero point position; S5. Test the full-band S-parameters of the filter to verify in-band insertion loss, out-of-band rejection, and high-end steepness; conduct temperature cycling and vibration tests to verify the performance stability of the filter under environmental stress; perform helium mass spectrometry leak detection on qualified products to ensure that the airtightness meets the requirements of high reliability applications.

5. The method for fabricating an improved waveguide filter according to claim 4, characterized in that, The ridge height of the single-ridge waveguide resonant cavity in step S1 satisfy: in, This represents the height of the waveguide cavity.

6. The method for fabricating an improved waveguide filter according to claim 4, characterized in that, The opening area of ​​the inductor diaphragm in step S3 satisfy: in, Waveguide wavelength is the characteristic impedance, and k is the coupling coefficient, with a value ranging from 0.05 to 0.

3.

7. The method for fabricating an improved waveguide filter according to claim 4, characterized in that, In step S4, the tuning accuracy of the tuning screw shall not be less than 0.

01. Furthermore, an iterative optimization algorithm is used to automate the tuning process.

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