Waveguide band-pass filter

Abstract

The invention relates to the field of radio frequency and microwave engineering, and discloses a waveguide band-pass filter which comprises an upper layer metal substrate and a lower layer metal substrate which are parallel to each other and opposite to each other, and the upper layer metal substrate and the lower layer metal substrate are spaced from each other in the vertical direction. Gradually-changed metal square column arrays arranged in the length direction of the lower-layer metal substrate are symmetrically arranged on the two sides, in the width direction of the lower-layer metal substrate, of the face, facing the upper-layer metal substrate, of the lower-layer metal substrate; a single row of periodic metal rectangular columns arranged in the length direction of the lower layer metal substrate and the upper layer metal substrate are arranged in the middle of the opposite surfaces of the lower layer metal substrate and the upper layer metal substrate in a mirror symmetry mode. And the height of the periodic metal rectangular column is increased, unchanged and then reduced. The band-pass filter provided by the invention is low in loss, and the passband width can be flexibly tuned.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency and microwave engineering, and in particular to a waveguide bandpass filter. Background Art

[0002] In RF and microwave communication systems, filters, as key components in the signal processing chain, are widely used in scenarios such as spectrum selection, signal shaping, and interference suppression. Traditional waveguide filters, due to their excellent quality factor and power handling, have significant advantages in the mid- and high-frequency bands. However, as communication systems evolve toward higher frequencies and wider bandwidths, filters have become increasingly dependent on performance metrics such as passband control accuracy, out-of-band rejection, and insertion loss, posing greater challenges to device structural design and manufacturing processes.

[0003] Common filter structures, such as LC filters, microstrip filters, and dielectric resonator filters, while mature and easy to manufacture, often suffer from increased losses, limited bandwidth, and poor structural adjustability in high-frequency applications. Therefore, a new filter solution with enhanced structural adjustability, lower losses, and suitability for high-frequency, broadband scenarios is urgently needed to promote its engineering application in next-generation communication systems. Summary of the Invention

[0004] The purpose of the present invention is to solve the above technical difficulties existing in the prior art and to provide a waveguide bandpass filter with low loss and flexibly adjustable passband width suitable for high-frequency communication scenarios.

[0005] To achieve the above-mentioned objectives, the present invention provides a waveguide bandpass filter, comprising an upper metal substrate and a lower metal substrate that are parallel to and opposite to each other, the upper metal substrate and the lower metal substrate being spaced apart from each other in the vertical direction, a surface of the lower metal substrate facing the upper metal substrate being symmetrically provided with a gradient metal square column array arranged along the length direction of the lower metal substrate on both sides in the width direction of the lower metal substrate, a single row of periodic metal rectangular columns arranged along the length direction of the lower metal substrate and the upper metal substrate being mirror-symmetrically provided in the middle of the opposing surfaces of the lower metal substrate and the upper metal substrate, the height of the periodic metal rectangular columns first increasing, then remaining unchanged, and then decreasing in the length direction of the lower metal substrate and the upper metal substrate, thereby forming a vertically symmetrical periodic structure having artificial surface plasmon characteristics.

[0006] Preferably, the upper metal substrate and the lower metal substrate have the same size.

[0007] Preferably, the lengths of the upper metal substrate and the lower metal substrate are The width is between 60.40mm and 62.80mm. The height is between 15.50mm and 17.90mm. All are between 1.80mm and 4.20mm.

[0008] Preferably, the distance between the upper metal substrate and the lower metal substrate is Between 3.3mm and 3.6mm.

[0009] Preferably, on both sides of the width direction of the lower metal substrate, the gradient metal square column array on each side includes two rows of metal square columns, and the two rows of metal square columns are arranged at equal intervals along the length direction and width direction of the lower metal substrate, and the heights of the metal square columns are equal; each row of metal square columns includes symmetrical first transition sections at both ends of the length direction of the lower metal substrate, and each first transition section includes three metal square columns; from the end to the middle of the length direction of the lower metal substrate, the distance between the three metal square columns and the long side edge of the lower metal substrate increases successively; the first transition sections at both ends of each row of metal square columns are the main periodic section, and the distance between each metal square column in the main periodic section of the outer row of metal square columns and the same long side edge of the lower metal substrate is equal, and Between 1.30mm and 1.40mm.

[0010] Preferably, the cross section of the metal square column is square with a side length of Between 1.00mm and 1.20mm, height Between 2.10mm and 2.50mm.

[0011] Preferably, the spacing between the two rows of metal square columns is The period of each row of metal square columns along the long side of the lower metal substrate is between 1.50mm and 1.80mm. Between 2.50mm and 2.90mm.

[0012] Preferably, at both ends of the lower metal substrate in the longitudinal direction, the inner rows of metal square columns of the gradient metal square column array on each side are opposite to each other, so as to form three groups of metal square columns in the first transition section; and from one end to the other end of the lower metal substrate in the longitudinal direction, the spacing between the three groups of metal square columns is: .

[0013] Preferably, the edges of each metal rectangular column in the periodic metal rectangular column along the length direction of the lower metal substrate and the upper metal substrate are The width of the lower metal substrate and the upper metal substrate is between 0.70 mm and 0.91 mm. The periodic length of the periodic metal rectangular column along the long side direction of the lower metal substrate and the upper metal substrate is between 1.00mm and 1.10mm. .

[0014] Preferably, along the length direction of the lower metal substrate and the upper metal substrate, the periodic metal rectangular column includes two second transition sections symmetrical to each other, each second transition section includes three metal rectangular columns arranged in sequence along the length direction of the lower metal substrate, and the height of the three metal rectangular columns from the end to the middle of the periodic metal rectangular column is calculated by the following formula: , where H Si is the height of the i-th metal rectangular column;

[0015] The area between the two second transition sections is a main period section, in which a plurality of metal rectangular columns of equal height are arranged. The height of the plurality of metal rectangular columns of equal height is Calculated by the following formula: ,in, is the free space wave number; is the propagation constant; is the periodic length of the periodic metal rectangular column along the length direction of the lower metal substrate and the upper metal substrate; is the side length of each metal rectangular column in the periodic metal rectangular columns along the length direction of the lower metal substrate and the upper metal substrate.

[0016] Preferably, the upper metal substrate, lower metal substrate, metal square pillar, and metal rectangular pillar of the bandpass filter are all made of copper, and the area between the upper metal substrate and the lower metal substrate is filled with air to form a low-dielectric-constant transmission environment. Compared with the prior art, the present invention has the following advantages:

[0017] The waveguide bandpass filter provided by the present invention includes an upper metal substrate and a lower metal substrate that are parallel to and opposite to each other. The upper metal substrate and the lower metal substrate are spaced apart from each other in the vertical direction. A gradient metal square column array arranged along the length direction of the lower metal substrate is symmetrically arranged on both sides of the side of the lower metal substrate facing the upper metal substrate in the width direction of the lower metal substrate, forming an electromagnetic bandgap structure, realizing non-contact waveguide transmission, suppressing stray mode propagation and reducing contact loss.

[0018] By adjusting specific geometric parameters in the electromagnetic bandgap structure (such as the height of the metal square pillar), the electromagnetic bandgap characteristics of the structure can be changed, and precise control of the lower cutoff frequency of the filter passband can be achieved.

[0019] To further enhance the passband control capability, the present invention, based on a non-contact waveguide, has a single row of periodic metal rectangular columns arranged along the length direction of the lower and upper metal substrates, mirror-symmetrically arranged in the middle of the mutually opposing surfaces of the lower and upper metal substrates. This constitutes an artificial surface plasmon propagation structure, which suppresses electromagnetic wave propagation in the high-frequency band and has the ability to control the cutoff frequency in the filter passband.

[0020] In order to improve the transmission efficiency of the above-mentioned artificial surface plasmon propagation structure, the height of the periodic metal rectangular columns is set in the present invention to first increase, then remain unchanged, and then decrease along the length direction of the lower metal substrate and the upper metal substrate. This can achieve efficient coupling and electromagnetic matching between different structures, thereby significantly reducing energy reflection and loss during transmission and improving energy transmission efficiency.

[0021] Through the collaborative design of these structures, the present invention achieves dual-parameter decoupled control of the upper and lower passband cutoff frequencies without requiring coordinated adjustments to multiple structural dimensions, significantly enhancing filter design flexibility and engineering adaptability. Furthermore, each structural segment utilizes a modular design, resulting in a compact and concise overall structure suitable for integration into high-density integrated systems and RF communication modules. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of the three-dimensional structure of a waveguide bandpass filter provided by an embodiment of the present invention.

[0023] Figure 2 This is a front view of a waveguide bandpass filter provided by an embodiment of the present invention.

[0024] Figure 3 for Figure 1 Schematic diagram of the three-dimensional structure when the lower metal substrate and the upper metal substrate are separated.

[0025] Figure 4 for Figure 1 The figure shows the main view of the upper metal substrate which only includes single-period metal rectangular columns.

[0026] Figure 5 for Figure 1 Top view of the middle and lower metal substrates.

[0027] Figure 6 This is an S-parameter diagram of the waveguide bandpass filter provided by an embodiment of the present invention.

[0028] Figure 7 is the period length of the periodic metal rectangular column Variation of S of waveguide bandpass filter 21 Influence diagram of parameters.

[0029] Figure 8is the height H of the metal rectangular column of the main period segment of the periodic metal rectangular column s Variation of S of waveguide bandpass filter 21 Influence diagram of parameters.

[0030] Figure 9 is the height of the metal square column Variation of S of waveguide bandpass filter 21 Influence diagram of parameters.

[0031] Among them, 1-lower metal substrate; 2-upper metal substrate; 3-gradient metal square column array; 4-periodic metal rectangular column. DETAILED DESCRIPTION

[0032] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0033] like Figure 1-Figure 5As shown, an embodiment of the present invention provides a waveguide bandpass filter, which includes an upper metal substrate 2 and a lower metal substrate 1 that are parallel to and opposite each other, the upper metal substrate 2 and the lower metal substrate 1 being spaced apart from each other in the vertical direction. A gradient metal square matrix 3 arranged along the length of the lower metal substrate 1 is symmetrically arranged on both sides of the side of the lower metal substrate 1 facing the upper metal substrate 2. The matrix is ​​used to achieve mode conversion and impedance matching and form an artificial electromagnetic bandgap structure, suppressing undesirable propagation modes and achieving contactless waveguide transmission. Adjusting the geometric parameters of the electromagnetic bandgap structure can change the electromagnetic bandgap characteristics of the structure, achieving precise control of the lower cutoff frequency of the filter passband. Based on a non-contact waveguide, a single row of periodic metal rectangular pillars 4, arranged along the length of the lower and upper metal substrates 1 and 2, are mirror-symmetrically arranged in the middle of the opposing surfaces of the lower and upper metal substrates 1 and 2, forming an artificial surface plasmon propagation structure. This structure suppresses electromagnetic wave propagation at high frequencies and has the ability to control the cutoff frequency within the filter passband. Along the length of the lower and upper metal substrates 1 and 2, the height of the periodic metal rectangular pillars 4 first increases, then remains constant, and then decreases. The metal pillar units, with their heights gradually varying at both ends, form a transition section, achieving efficient coupling and electromagnetic matching between the different structures, significantly reducing energy reflection and loss during transmission. The present invention combines a non-contact waveguide with a top-to-bottom symmetrical periodic metallic rectangular prism (4) exhibiting artificial surface plasmon properties. By adjusting specific geometric parameters of the non-contact waveguide structure (such as the height of the prisms), the lower passband cutoff frequency can be independently controlled. Adjusting specific geometric parameters of the periodic metallic rectangular prisms (such as the period or height) allows for independent control of the upper passband cutoff frequency. This design not only enables independent adjustment of the upper and lower passband limits but also achieves bidirectional decoupled tuning of the passband boundaries, eliminating the need for coordinated adjustments of multiple structural dimensions. This significantly enhances filter design flexibility and engineering adaptability.

[0034] The upper metal substrate 2 and the lower metal substrate 1 have the same size; the length of the upper metal substrate 2 and the lower metal substrate 1 The width is between 60.40mm and 62.80mm. The height is between 15.50mm and 17.90mm. The distance h between the upper metal substrate 2 and the lower metal substrate 1 is between 1.80 mm and 4.20 mm. d Between 3.30mm and 3.60mm.

[0035] On both sides of the width direction of the lower metal substrate 1, the gradient metal square column array 3 on each side includes two rows of metal square columns, and the two rows of metal square columns are evenly spaced along the length direction and width direction of the lower metal substrate 1, and the height of each metal square column is equal; each row of metal square columns includes a symmetrical first transition section at both ends of the length direction of the lower metal substrate 1, and each first transition section includes three metal square columns; from the end to the middle of the length direction of the lower metal substrate 1, the distance between the three metal square columns and the long side edge of the lower metal substrate 1 increases successively; the main period section is between the first transition sections at both ends of each row of metal square columns, and the structural parameters of the metal square columns within the main period section are the same, which is used to set the lower cutoff frequency. The distance between each metal square column within the main period section of the outer row of metal square columns and the same long side edge of the lower metal substrate 1 equal, and Between 1.30mm and 1.40mm.

[0036] The cross section of the metal square column is square, with a side length of Between 1.00mm and 1.20mm, height The distance between the two rows of metal square columns is between 2.10mm and 2.50mm. The period length of each row of metal square columns along the long side direction of the lower metal substrate 1 is between 1.50mm and 1.80mm. .

[0037] At both ends of the lower metal substrate 1 in the longitudinal direction, the inner rows of metal square columns of the gradient metal square column array 3 on each side are opposite to each other, so as to form three groups of metal square columns in the first transition section; from one end to the other end of the lower metal substrate 1 in the longitudinal direction, the spacing between the three groups of metal square columns is:

[0038] In an embodiment of the present invention, the gradient metal square column array 3 constructs a main periodic segment by an array of metal square columns symmetrically distributed along the longitudinal direction, and sets a gradient transition structure at its end to optimize the waveguide mode conversion. Adjusting the structure size can be used to set the lower cutoff frequency of the passband; and the main periodic segment of the middle periodic metal rectangular column 4 is composed of a row of regularly arranged metal units, and is also provided with a transition structure for impedance matching and mode matching. Its main periodic segment is used to suppress high-frequency transmission, thereby setting the upper cutoff frequency of the passband.

[0039] The edges of each metal rectangular column in the periodic metal rectangular column 4 along the length direction of the lower metal substrate 1 and the upper metal substrate 2 are The width of the lower metal substrate 1 and the upper metal substrate 2 is between 0.70 mm and 0.91 mm. The periodic length of the periodic metal rectangular column 4 along the long side direction of the lower metal substrate 1 and the upper metal substrate 2 is between 1.00mm and 1.10mm.

[0040] Along the length direction of the lower metal substrate 1 and the upper metal substrate 2, the periodic metal rectangular column 4 includes two second transition sections symmetrical to each other, and each second transition section includes three metal rectangular columns arranged in sequence along the length direction of the lower metal substrate 1. From the end to the middle of the periodic metal rectangular column 4, the height of the three metal rectangular columns is calculated by the following formula: , where H Si is the height of the i-th metal rectangular column;

[0041] The area between the two second transition sections is a main period section, in which a plurality of metal rectangular columns of equal height are arranged. The height of the plurality of metal rectangular columns of equal height is Calculated by the following formula: ,in, is the free space wave number; is the propagation constant; is the periodic length of the periodic metal rectangular column along the long side direction of the lower metal substrate 1 and the upper metal substrate 2; The length of each metal rectangular column in the periodic metal rectangular column along the length direction of the lower metal substrate 1 and the upper metal substrate 2; the structural parameters of each metal rectangular column in the main period segment are consistent, which is used to effectively suppress high-frequency components and set the upper cutoff frequency. By changing the height of the multiple metal rectangular columns of equal height The bandwidth tunable function of the bandpass filter can be achieved.

[0042] The upper metal substrate 2, the lower metal substrate 1, the gradient metal square column array 3 and the periodic metal rectangular column 4 of the bandpass filter are all made of metal copper, and the area between the upper metal substrate and the lower metal substrate is filled with air.

[0043] See also Figure 7-Figure 9 By adjusting the structural size design of the bandpass filter, the S of the bandpass filter can be changed. 21 parameter.

[0044] The embodiment of the present invention combines the gradient metal square column array 3 with the periodic metal rectangular column 4, and the two are designed in a coordinated manner to achieve bidirectional independent regulation of the passband boundary while ensuring transmission efficiency, and effectively reduce reflection and stray mode interference. Specifically,

[0045] The lower cutoff frequency of the passband is achieved by adjusting the structural dimensions of the main periodic segment of the gradient metal square column array 3; the upper cutoff frequency is achieved by adjusting the geometric parameters of the periodic unit in the main periodic segment of the embedded periodic structure segment. The two can be controlled independently, thereby achieving a bandwidth adjustment capability of approximately 29.1% (29.05–32.87 GHz).

[0046] Compared with traditional waveguide filter structures, the embodiments of the present invention have better adjustability and engineering practicality, and are suitable for filtering applications in high-frequency communications and millimeter-wave systems.

[0047] Through simulation experiments, the technical solution provided by the embodiment of the present invention significantly reduces energy reflection and loss during transmission. The simulation results show that the return loss is better than 18dB.

[0048] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made. This includes combining the specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple variations and combinations should also be considered as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A waveguide bandpass filter, characterized in that: The bandpass filter includes an upper metal substrate and a lower metal substrate that are parallel to and opposite to each other. The upper metal substrate and the lower metal substrate are spaced apart from each other in the vertical direction. A gradient metal square column array arranged along the length direction of the lower metal substrate is symmetrically arranged on both sides of the width direction of the lower metal substrate on a side of the lower metal substrate facing the upper metal substrate. A single row of periodic metal rectangular columns arranged along the length direction of the lower metal substrate and the upper metal substrate is mirror-symmetrically arranged in the middle of the opposing surfaces of the lower metal substrate and the upper metal substrate. In the length direction of the lower metal substrate and the upper metal substrate, the height of the periodic metal rectangular columns first increases, then remains unchanged, and then decreases.

2. The waveguide bandpass filter according to claim 1, wherein The upper metal substrate and the lower metal substrate have the same size: the length of the upper metal substrate and the lower metal substrate 60.40-62.80mm, width 15.50-17.90mm, height 1.80-4.20mm.

3. The waveguide bandpass filter according to claim 1, wherein The distance between the upper metal substrate and the lower metal substrate It is 3.30mm-3.60mm.

4. The waveguide bandpass filter according to claim 1, wherein On both sides of the width direction of the lower metal substrate, the gradient metal square column array on each side includes two rows of metal square columns, and the two rows of metal square columns are arranged at equal intervals along the length direction and width direction of the lower metal substrate, and the heights of the metal square columns are equal; each row of metal square columns includes symmetrical first transition sections at both ends of the length direction of the lower metal substrate, and each first transition section includes three metal square columns; from the end to the middle of the length direction of the lower metal substrate, the distance between the three metal square columns and the long side edge of the lower metal substrate increases successively; the main period section is between the first transition sections at both ends of each row of metal square columns, and the distance between each metal square column in the main period section of the outer row of metal square columns and the long side edge is equal, and It is 1.30-1.40mm.

5. The waveguide bandpass filter according to claim 4, wherein: The cross section of the metal square column is square, with a side length of 1.00-1.20mm, height 2.10-2.50mm.

6. The waveguide bandpass filter according to claim 4, wherein: The spacing between the two rows of metal square columns The period of each row of metal square columns along the long side of the lower metal substrate is 1.50-1.80 mm. 2.50-2.90mm.

7. The waveguide bandpass filter according to claim 4, wherein: At both ends of the length direction of the lower metal substrate, the inner rows of metal square columns of the gradient metal square column array on each side are opposite to each other, so as to form three groups of metal square columns in the first transition section; from one end to the other end of the length direction of the lower metal substrate, the spacing between the four groups of metal square columns is =7.00-7.20mm, =6.40-6.80mm, =6.00-6.20mm.

8. The waveguide bandpass filter according to claim 1, wherein The edges of each metal rectangular column in the periodic metal rectangular column along the length direction of the lower metal substrate and the upper metal plate are The width of the lower metal substrate and the upper metal plate is 0.70-0.91 mm. The periodic length of the periodic metal rectangular column along the length direction of the lower metal substrate and the upper metal plate is 1.00-1.1 mm.

9. The waveguide bandpass filter according to claim 8, wherein Along the length direction of the lower metal substrate and the upper metal plate, the periodic metal rectangular column includes two second transition sections symmetrical to each other, and each second transition section includes three metal rectangular columns arranged in sequence along the length direction of the lower metal substrate. From the end to the middle of the periodic metal rectangular column, the height of the three metal rectangular columns is calculated by the following formula: , where H Si is the height of the i-th metal rectangular column; The area between the two second transition sections is a main period section, in which a plurality of metal rectangular columns of equal height are arranged. The height of the plurality of metal rectangular columns of equal height is Calculated by the following formula: ,in, is the free space wave number; is the propagation constant; is the periodic length of the periodic metal rectangular column along the length direction of the lower metal substrate and the upper metal plate; is the side length of each metal rectangular column in the periodic metal rectangular columns along the length direction of the lower metal substrate and the upper metal plate.

10. The waveguide bandpass filter according to claim 1, wherein: The upper metal substrate, the lower metal substrate, the metal square column and the metal rectangular column in the bandpass filter are all made of metal copper. A cavity is formed between the upper metal substrate and the lower metal substrate, and the cavity contains air medium.

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