Bandwidth-controllable compact ridge waveguide cavity bandpass filter based on sspp and manufacturing method thereof

Abstract

This invention discloses a bandwidth-controllable compact ridge waveguide cavity bandpass filter based on SSPP and its fabrication method. The device includes a cavity containing a ridge waveguide. Several inverted T-shaped grooves are etched at intervals on the ridge waveguide, forming a structure where the middle section is an artificial surface plasmon polariton (SSPP) and the left and right ends are transitional SSPP structures. The transitional SSPP structures at the left and right ends are respectively connected to horizontal coaxial connectors. Dual grating structures are respectively provided on both sides of the ridge waveguide within the cavity. This invention achieves a wideband bandpass structure of 7.6GHz–12.4GHz by integrating the ridge waveguide, SSPP, and dual gratings into a single cavity. It achieves a return loss below -16dB and an insertion loss of 0.23dB within the band. Low loss and small size are achieved within a 44.8% wideband, and the passband bandwidth can be flexibly tuned.

Description

Technical Field

[0001] This invention belongs to the field of bandpass filter design, and particularly relates to a bandwidth-controllable compact ridge waveguide cavity bandpass filter based on SSPP and its fabrication method. Background Technology

[0002] Artificial surface plasmon polaritons (SSPPs) are periodic structures that can support the propagation of surface waves with short operating wavelengths and near-field confinement. Based on their inherent low-pass characteristics, SSPPs are widely used in the fabrication of bandpass filters. Existing SSPP filters utilize microstrip lines, substrate-integrated waveguides, rectangular waveguides, and gapped waveguides to implement SSPP filter designs. With the development of communication technology, the demand for miniaturization and low loss in bandpass filters has gradually increased. Waveguide structures, due to their low loss and high power capacity, are widely used in the design of high-frequency systems. Among them, ridge waveguides, due to their lower cutoff frequency than waveguides of the same size, are beneficial for achieving circuit miniaturization while obtaining a wider single-mode operating bandwidth.

[0003] In existing technologies, loading periodic metal strips onto microstrip transmission lines and substrate-integrated waveguides results in high structural losses, making it difficult to meet the requirements for low-loss applications. Furthermore, loading periodic metal pillars into rectangular waveguides and gapped waveguides produces long transition structures, which cannot meet the requirements for small dimensions. Summary of the Invention

[0004] Objective of the Invention: The objective of this invention is to provide a bandwidth-controllable compact ridge waveguide cavity bandpass filter based on SSPP and its fabrication method. A wideband bandpass structure of 7.6GHz-12.4GHz is achieved by integrating the ridge waveguide, SSPP, and dual gratings into a single cavity. Return loss below -16dB and insertion loss of 0.23dB are achieved within the band. Low loss and small size are realized within a 44.8% wideband, and the bandwidth can be flexibly tuned.

[0005] Technical Solution: The present invention discloses a bandwidth-controllable compact ridge waveguide cavity bandpass filter based on SSPP, comprising a cavity, wherein a ridge waveguide is provided within the cavity, and several inverted T-shaped grooves are etched at intervals on the ridge waveguide to form a structure in which the middle section is an artificial surface plasmon polariton (SSPP) and the left and right ends are transitional SSPP structures, the transitional SSPP structures at the left and right ends are respectively connected to horizontal coaxial connectors; a dual grating structure is provided on both sides of the ridge waveguide within the cavity.

[0006] Furthermore, the intermediate segment artificial surface plasmon polariton (SSPP) structure is as follows:

[0007] An inverted T-shaped groove is etched downwards on the ridge, with a depth (hs) that can vary from 2 mm to 4.6 mm, an upper width (d) that can vary from 0.4 mm to 1.2 mm, and a lower width (ls) that can vary from 1.5 mm to 3.3 mm.

[0008] Furthermore, the transitional artificial surface plasmon polariton (SSPP) structure is as follows:

[0009] Based on the artificial surface plasmon polariton SSPP in the middle section, the depth is gradually reduced to both sides in 0.5mm increments. The feasible range for depth (hs1) is 1.5mm-4.1mm, the feasible range for depth (hs2) is 1mm-3.6mm, and the feasible range for width (d) is 0.4mm-1.2mm.

[0010] Furthermore, the dimensions of the cavity are:

[0011] The cavity length L is 30-32mm, the width W is 12.3-13mm, and the height H is 5.5-6mm.

[0012] Furthermore, the dimensions of the inverted T-shaped groove are:

[0013] The depth (hs) of the inverted T-groove can vary from 2mm to 4.6mm, the upper width (d) can vary from 0.4mm to 1.2mm, and the lower width (ls) can vary from 1.5mm to 3.3mm.

[0014] Furthermore, the dual-grating structure is specifically as follows:

[0015] Stepped grating structures of the same height as the cavity are loaded on both sides of the cavity. The length (lg) of the three middle gratings can vary from 0.8mm to 4mm, and the width (wg) can vary from 0.5mm to 3mm. The lengths of the other two sides decrease in increments of 0.3mm.

[0016] Furthermore, the filter is made of aluminum.

[0017] This invention also discloses a method for fabricating a bandwidth-controllable compact ridge waveguide cavity bandpass filter based on SSPP, comprising the following steps:

[0018] Step 1: Determine the cavity and internal ridge dimensions of the ridge waveguide based on the center frequency of the target operating frequency band, so that the ridge waveguide operates at TE within the target frequency band. 10 model;

[0019] Step 2: Etch a T-shaped groove downwards on the ridge waveguide to achieve bandpass characteristics. The upper cutoff frequency can be independently controlled by adjusting the depth and width of the groove.

[0020] Step 3: Determine the order and size of the double grating. By adjusting the order and extension length of the double grating, the lower cutoff frequency can be controlled.

[0021] Step 4: Optimize the relevant parameters to achieve the best matching result.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0023] (1) This invention successfully designed a low-loss cavity bandpass filter with adjustable passband bandwidth by etching inverted T-grooves on a ridge waveguide, and explored the characteristics of the SSPP. Independent control of the passband bandwidth was achieved by using an SSPP on the ridge of the ridge waveguide and loading dual gratings on both sides of the ridge, effectively adjusting the upper and lower cutoff frequencies of the filter passband. Furthermore, the ridge waveguide has low impedance and can be directly connected to a coaxial connector, resulting in a more compact overall size. A wideband bandpass structure of 7.6GHz-12.4GHz was achieved by integrating the ridge waveguide, SSPP, and dual gratings into a single cavity. Return loss below -16dB and insertion loss of 0.23dB were achieved within the band. Low loss and small size were achieved within a 44.8% wideband, and the bandwidth can be flexibly tuned.

[0024] (2) This invention utilizes SSPP to design a broadband ridge waveguide cavity bandpass filter. Compared to SSPP bandpass filters fabricated on dielectric substrates, this design exhibits lower loss. Compared to filters designed with other metal waveguides, this design, employing the unique structure of ridge waveguides, is easier to achieve various shape requirements and is easier to manufacture. Integrating the ridge waveguide, SSPP, and dual gratings into a single cavity solves the problem of large metal waveguide size. Due to the dual gratings loaded on both sides of the ridge, flexible and independent frequency band control can be achieved. In terms of performance, the bandwidth-controllable ridge waveguide cavity bandpass filter described in this invention achieves an insertion loss of less than 0.23 dB, a bandwidth of up to 44.8%, and a return loss of less than -16 dB within the operating frequency band.

[0025] (3) This invention has a wide range of applications. In communication systems, a bandpass filter is a device that allows signal transmission within a specific frequency range while blocking other frequency ranges. It can selectively transmit waves in a specific frequency band. In radar systems, bandpass filters are used to select a specific frequency range in radar echoes to detect the position and velocity of targets. This is crucial for target identification and tracking. In sonar systems, bandpass filters can select echoes within a specific frequency range in acoustic signals for detecting and identifying underwater targets. Attached Figure Description

[0026] Figure 1 This is a 3D structural diagram of the present invention;

[0027] Figure 2 This is a side view of the present invention;

[0028] Figure 3 Top view of the present invention Figure 1 ;

[0029] Figure 4 This is a schematic diagram of the structure of the present invention;

[0030] Figure 5 Top view of the present invention Figure 2 ;

[0031] Figure 6 Schematic diagram of SSPP and transition SSPP structure;

[0032] Figure 7 The S-parameter plot of the bandpass filter;

[0033] Figure 8 Insertion loss plot;

[0034] Figure 9 For depth changes to S 21 Impact diagram;

[0035] Figure 10 For the change of SSPP width on S 21 Impact diagram;

[0036] Figure 11 For the effect of grating length variation on S 21 Impact diagram;

[0037] In the figure, 1 is the ridge waveguide, 2 is the inverted T-groove, 3 is the dual grating structure, and 4 is the horizontal coaxial transition connector. Detailed Implementation

[0038] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0039] Figure 1-3 The diagram shows a 3D structural diagram, side view, and top view of an SSPP bandpass filter, including inverted T-shaped grooves etched on the ridge to form the SSPP structure. Progressive depths hs1 and hs2 serve as transitional SSPP sections, and dual grating structures are loaded on both sides of the ridge. The ridge waveguide is fed using a horizontal coaxial connector. The entire invention is made of aluminum.

[0040] The design process involves determining the initial dimensions of the ridge waveguide based on the center frequency. Then, utilizing the low-pass characteristics of the SSPP (SSide-Side Plate Filter), a corresponding inverted T-shaped slot is designed on the ridge to form the SSPP structure, controlling the upper cutoff frequency of the band, and optimization is performed. Subsequently, the high-pass characteristics of the dual-grating structure are used to adjust the upper cutoff frequency of the band, integrating the two structures into a single cavity to achieve the function of a bandpass filter. This invention employs a coaxial-to-ridge waveguide transition scheme as shown in structure 4, and... Figure 4 The transition grooves at both ends of the ridge are designed to achieve wideband impedance matching.

[0041] like Figure 6 As shown, this invention has two ports. The signal is input from port 1, passes through a coaxial cable to the ridge waveguide, then passes through a transitional SSPP to the middle SSPP for impedance matching, and finally the signal is output from port 2. First, the dimensions of the ridge waveguide are determined based on the center frequency, and then an SSPP with low-pass characteristics is loaded to form the upper stopband. The ridge waveguide and SSPP themselves can achieve bandpass characteristics. To allow for arbitrary adjustment of the lower cutoff frequency and controllable bandwidth, this design introduces dual gratings on both sides of the ridge waveguide, thereby enabling the design of a bandpass filter with controllable bandwidth.

[0042] The simulation results of this example study on the design of a low-loss cavity bandpass filter with controllable bandwidth using SSPP loaded on a ridge waveguide are shown below. Figure 7-11 The center frequency is f0 = 10 GHz, the frequency range is 7.6 GHz - 12.4 GHz, where S11 is less than -16 dB and the insertion loss is less than 0.23 dB.

[0043] Design steps for a bandpass filter made using SSPP and dual gratings:

[0044] Step 1: Determine the dimensions of the ridge waveguide. The dimensions of the ridge waveguide cavity and its internal ridge are determined by the center frequency of the target operating frequency band. This ensures the ridge waveguide operates at TE within the target frequency band. 10 model.

[0045] Step 2: The second step involves etching a T-shaped groove downwards on the ridge waveguide to achieve bandpass characteristics. The upper cutoff frequency can be independently controlled by adjusting the groove depth and width. A suitable groove depth and width are found through adjustment (in this design, the groove depth hs is 4.1 mm, the upper width d is 1 mm, and the lower width ls is 2 mm).

[0046] Step 3: The third step is to determine the order and size of the double grating. By adjusting the order and extension length of the double grating, the lower cutoff frequency can be controlled (in this design, the grating length lg is 2.5mm, and gratings with transition lengths lg1 and lg2 are used for transition).

[0047] Step four: The relevant parameters are optimized to achieve the best matching result, as shown in Table 1.

[0048] Table 1

[0049] parameter W w H h Th Tl hs Value (mm) 12.3 3.7 5.5 4.7 2.5 2 4.1 parameter <![CDATA[hs1]]> <![CDATA[hs2]]> ls ws <![CDATA[ws1]]> ps d Value (mm) 3.6 3.1 2 1 0.8 2.5 1 parameter c wg pg lg <![CDATA[lg1]]> <![CDATA[lg2]]> R Value (mm) 25 1.6 1.8 2.5 2.2 1.9 2 parameter L Value (mm) 31

Claims

1. A bandwidth-controllable compact ridge waveguide cavity bandpass filter based on SSPP, characterized in that, The device includes a cavity, within which a ridge waveguide (1) is provided. Several inverted T-shaped grooves (2) are etched at intervals on the ridge waveguide (1) to form a middle section of artificial surface plasmon polariton (SSPP). The left and right ends are transitional SSPP structures, which are respectively connected to a horizontal coaxial connector (4). A double grating structure (3) is provided on both sides of the ridge waveguide (1) within the cavity. The intermediate segment artificial surface plasmon polariton (SSPP) structure is as follows: An inverted T-shaped groove (2) is etched downwards on the ridge waveguide (1) to a depth of hs The width is 2mm-4.6mm, and the top width is... d The width is 0.4mm-1.2mm, and the bottom width is... ls The thickness ranges from 1.5mm to 3.3mm. The transitional artificial surface plasmon polariton (SSPP) structure is as follows: Based on the artificial surface plasmon polariton SSPP in the middle section, the depth is gradually reduced towards both sides in 0.5mm increments. hs 1 is 1.5mm-4.1mm deep. hs 2 is 1mm-3.6mm in width. d The thickness ranges from 0.4mm to 1.2mm.

2. The bandwidth-controllable compact ridge waveguide cavity bandpass filter based on SSPP according to claim 1, characterized in that, The dimensions of the cavity are: cavity length L 30-32mm, width W For 12.3-13mm and height H It is 5.5-6mm.

3. The bandwidth-controllable compact ridge waveguide cavity bandpass filter based on SSPP according to claim 1, characterized in that, The dimensions of the inverted T-groove (2) are: Depth of the inverted T-groove hs The width is 2mm-4.6mm, and the top width is... d The width is 0.4mm-1.2mm, and the bottom width is... ls The thickness ranges from 1.5mm to 3.3mm.

4. A bandwidth-controllable compact ridge waveguide cavity bandpass filter based on SSPP according to claim 1, characterized in that, The specific structure of the dual grating structure (3) is as follows: A stepped grating structure of the same height as the cavity is loaded on both sides of the cavity, and the three gratings in the middle have a depth of [length missing]. lg The width is 0.8mm-4mm. wg The length is 0.5mm-3mm, and the lengths of the other two sides decrease in increments of 0.3mm.

5. A bandwidth-controllable compact ridge waveguide cavity bandpass filter based on SSPP according to claim 1, characterized in that, The filter is made of aluminum.

6. A method for fabricating a bandwidth-controllable compact ridge waveguide cavity bandpass filter based on claim 1, characterized in that, Includes the following steps: Step 1: Determine the cavity and internal ridge dimensions of the ridge waveguide based on the center frequency of the target operating frequency band, so that the ridge waveguide operates at TE within the target frequency band. 10 model; Step 2: Etch a T-shaped groove downwards on the ridge waveguide to achieve bandpass characteristics. The upper cutoff frequency can be independently controlled by adjusting the depth and width of the groove. Step 3: Determine the order and size of the double grating. By adjusting the order and extension length of the double grating, the lower cutoff frequency can be controlled. Step 4: Optimize the relevant parameters to achieve the best matching result.

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