T-shaped dielectric coaxial resonator and wide-stop-band band-pass filter

Abstract

The T-shaped dielectric coaxial resonator comprises a T-shaped section dielectric waveguide, a metalized blind hole is formed in the center of the top face of the horizontal portion of the T-shaped section dielectric waveguide, and all the outer surfaces of the T-shaped section dielectric waveguide are coated with silver. The wide-stop-band band-pass filter based on the T-shaped dielectric coaxial resonators comprises a plurality of linearly arranged T-shaped dielectric coaxial resonators, and the adjacent T-shaped dielectric coaxial resonators are connected through coupling windows to form an integrated structure. And feed blind holes are formed in the centers of the bottom surfaces of the vertical parts of the T-shaped dielectric coaxial resonators at the two ends of the integrated structure. According to the T-shaped dielectric coaxial resonator, the dominant mode frequency is regulated and controlled through the size of the metalized blind hole, and harmonic waves are pushed away to a higher frequency band by means of the T-shaped structure, so that the stop-band suppression range is remarkably widened. The band-pass filter based on the resonator has the characteristics of miniaturization, wide passband, low insertion loss and excellent out-of-band rejection.

Description

Technical Field

[0001] This invention relates to a communication device component, and more particularly to a wide stopband bandpass filter. Background Technology

[0002] Against the backdrop of the technological evolution from 5G-A to 6G, base station filters face an urgent need for multi-dimensional performance upgrades: while continuously pursuing miniaturization, lightweight design, low loss, and low cost, wide stopband performance has become a key indicator in system design. Although traditional dielectric waveguide filters offer advantages such as low loss and high Q-value, their stopband width is often limited by higher-order modes and parasitic passbands, making it difficult to meet the stringent requirements of future communication systems for spectral purity and anti-interference capabilities. With increasingly scarce spectrum resources and continuously improving equipment integration, effectively expanding the stopband range while maintaining the excellent passband performance of dielectric filters has become a core challenge in next-generation filter design. Wide stopband design helps reduce the use of additional filtering circuits, promotes further miniaturization of equipment, and reduces system complexity and overall power consumption.

[0003] Currently, research on dielectric waveguide filters with wide stopband characteristics is still in the exploratory stage, especially in the synergistic optimization of structural simplicity, fabrication feasibility, and wide stopband performance, where mature and reliable solutions are still lacking. The main shortcomings of existing technologies can be summarized as follows: First, traditional dielectric waveguide resonators typically operate in the fundamental mode, and their stopband width is limited by the dense distribution of higher-order modes. Even by optimizing the coupling structure or introducing external suppression circuits, it is still difficult to achieve a wide stopband suppression effect covering multiple octaves without significantly degrading the passband performance.

[0004] Second, although dielectric waveguides inherently possess miniaturization characteristics, auxiliary structures introduced to extend the stopband (such as parasitic resonant units and additional filter links) often occupy more space. This not only diminishes the original size advantage of dielectric waveguides but also makes the overall structure more complex, significantly increasing the difficulty of electromagnetic analysis, simulation modeling, and performance optimization. Summary of the Invention

[0005] Objective of the Invention: To address the aforementioned limitations of existing technologies, this invention proposes a T-type dielectric coaxial resonator that achieves both structural miniaturization and a significantly wide stopband characteristic. Another objective of this invention is to propose a wide stopband bandpass filter based on a T-type dielectric coaxial resonator, which significantly improves the stopband rejection range while maintaining low insertion loss and compact size, thus combining the advantages of wide passband, high rejection, miniaturization, and low loss.

[0006] Technical solution: A T-type dielectric coaxial resonator, comprising: a T-shaped cross-section dielectric waveguide, wherein a metallized blind hole is provided at the center of the top surface of the horizontal portion of the T-shaped cross-section dielectric waveguide, and all outer surfaces of the T-shaped cross-section dielectric waveguide are silver-coated.

[0007] Furthermore, the lower half of the T-section dielectric waveguide is a rectangular dielectric waveguide with a height of [missing information]. h l The waveguide narrows symmetrically inward along its width, forming ridges on both sides with a width of [missing information]. w The T-shaped structure.

[0008] Furthermore, the fundamental mode resonant frequency of the T-type dielectric coaxial resonator is determined by the height of the metallized blind via. h r Regulation.

[0009] Furthermore, the first higher-order mode frequency of the T-shaped dielectric coaxial resonator is determined by the width of the ridges on both sides of the T-shaped cross-section dielectric waveguide. w Regulation.

[0010] A wide stopband bandpass filter based on the T-type dielectric coaxial resonator, the filter comprising a plurality of the T-type dielectric coaxial resonators and a plurality of coupling windows; the plurality of T-type dielectric coaxial resonators are arranged linearly, and adjacent T-type dielectric coaxial resonators are connected by coupling windows located between them to form an integral structure; a feed blind hole is provided at the center of the bottom surface of the vertical part of the T-type dielectric coaxial resonator located at both ends of the integral structure, and a non-metallic ring concentric with the feed blind hole is also provided on the bottom surface.

[0011] Furthermore, the dielectric structure of the bandpass filter is an integral structure made of sintered ceramic material, and the outer surface of the dielectric structure, except for the non-metallized ring, is coated with silver.

[0012] Furthermore, the resonant frequency of the bandpass filter is adjusted by the metallized blind holes of each of the T-type dielectric coaxial resonators.

[0013] Furthermore, the coupling strength between adjacent T-type dielectric coaxial resonators is determined by the length of the coupling window. l cw Adjustment, the length of the coupling window l cw The length is the length in the direction perpendicular to the linear arrangement direction.

[0014] Furthermore, the quality factor of the bandpass filter Q e Through the height of the power supply blind hole h p adjust.

[0015] Beneficial Effects: The T-shaped dielectric coaxial resonator proposed in this invention innovates upon the traditional rectangular waveguide structure by dividing it into upper and lower parts along its height. The lower half of the waveguide is symmetrically reduced inward along its width, thus forming a planar T-shaped structure. Simultaneously, a metallized blind via is etched at the center of the upper surface of the resonator, forming a dielectric coaxial resonator unit. This design controls the dominant mode frequency by adjusting the size of the metallized blind via and pushes harmonics to higher frequencies using the T-shaped structure, significantly widening the stopband suppression range while achieving structural miniaturization.

[0016] The wide stopband bandpass filter based on this T-type dielectric coaxial resonator, compared with existing coaxial bandpass filters, can significantly improve the stopband rejection range while maintaining low insertion loss and compact size, and has the comprehensive advantages of wide passband, high rejection, miniaturization and low loss. Attached Figure Description

[0017] Figure 1 This is a three-dimensional structural diagram of the T-type dielectric coaxial resonator of the present invention; Figure 2 This is a three-dimensional structural diagram of an embodiment of the wide stopband bandpass filter based on a T-type dielectric coaxial resonator according to the present invention; Figure 3 This is a plan view of an embodiment of the wide stopband bandpass filter based on a T-type dielectric coaxial resonator according to the present invention; Figure 4 Three-dimensional structural diagrams of three different types of resonators are shown, where (a) is a traditional rectangular dielectric waveguide resonator, (b) is a T-type dielectric coaxial resonator with a blind hole at the bottom, and (c) is a T-type dielectric coaxial resonator with a blind hole at the top. Figure 5 The height of the metallized blind hole in the T-type dielectric coaxial resonator of this invention. h r Simulation results for the effects of the first two modes, where (a) corresponds to the resonant frequency and (b) corresponds to the unloaded quality factor. Q u ; Figure 6 The ridge width of the T-type dielectric coaxial resonator of this invention w Simulation results for the effects of the first two modes, where (a) corresponds to the resonant frequency and (b) corresponds to the unloaded quality factor. Q u ; Figure 7 This is a coupled topology diagram of the fourth-order wide-stopband bandpass filter based on a T-type dielectric coaxial resonator according to the present invention; Figure 8 The following are the S-parameter simulation results of the fourth-order wide stopband bandpass filter based on the T-type dielectric coaxial resonator of this invention, where (a) corresponds to 2.1~3.1GHz and (b) corresponds to 2~8GHz; Figure 9 The coupling coefficient between adjacent resonators of the wide stopband bandpass filter of this invention. k With the length of the coupling window l cw The curve of change; Figure 10 The external quality factor of the wide stopband bandpass filter of this invention Q e With the height of the blind hole for power supply h p The curve showing the change. Detailed Implementation

[0018] The invention will now be further explained with reference to the accompanying drawings. Example

[0019] A T-type dielectric coaxial resonator, its three-dimensional structure is as follows: Figure 1 As shown. All outer surfaces of this resonator are silver-coated. First, the lower half of the rectangular dielectric waveguide is [height missing]. h l The waveguide narrows symmetrically inward along its width, forming ridges on both sides with a width of [missing information]. w A T-shaped cross-section dielectric waveguide is used; at the same time, a metallized blind hole is etched at the center of its upper surface, together forming a complete coaxial dielectric waveguide resonant unit.

[0020] Figure 4 (a) shows a conventional rectangular dielectric waveguide resonator with a height of [missing information] etched at the center of its lower surface. h r Metallized blind holes. Based on this structure, the resonator is placed along the height... h Directional partitioning, and the height is h l The two side walls of the lower half along the width a Inward symmetrical width w That is, to obtain Figure 4 The T-type dielectric coaxial resonator shown in (b). Further, if the height is... h r When the metallized blind hole moves from the bottom surface to the top surface of the resonator, it forms... Figure 4 The structure shown in (c) illustrates this. Through this series of structural evolutions, the cavity mode is gradually pushed to higher frequency bands, causing the original first higher-order mode to change from the cavity mode to the second mode on the coaxial axis, thereby effectively extending the stopband.

[0021] To verify the above theoretical analysis and more clearly demonstrate the performance advantages of this T-type dielectric coaxial resonator, Table 1 compares... Figure 4Three resonators with identical external dimensions and metallized blind aperture heights are shown. Results indicate that this resonator not only has the lowest fundamental mode resonant frequency but also the largest frequency ratio between its first higher-order mode and the fundamental mode (approximately 2.89 times). It achieves both structural miniaturization and significant wide stopband characteristics, making it a preferred option for compact filter design.

[0022] Table 1

[0023] Figure 5 Demonstrates the ability to change only the height of the power supply blind hole h r Simulation results of resonant frequency and unloaded quality factor at that time. With blind hole... h r As the load increases, the fundamental mode resonant frequency decreases significantly, while the frequency of the first higher-order mode remains essentially unchanged, and the unloaded quality factor of both modes decreases. The reason for the decrease in the fundamental mode frequency is that the electric field of the main mode is mainly concentrated between the metallized blind hole and the bottom surface. The gap between the two is equivalent to a capacitor. As the gap decreases, the capacitance increases, and the resonant frequency decreases. Figure 6 To change only the width of the spine on both sides w Simulation results show that the frequency of the first higher-order mode increases slightly, while the fundamental mode frequency and the unloaded quality factors of both remain essentially unchanged. This is because the electric field of the first higher-order mode (the coaxial secondary mode) is mainly concentrated at the bottom of the blind aperture and its axial midpoint: near the axial midpoint, the discontinuity of the waveguide structure results in a large distance between the outer walls on both sides, equivalent to a small capacitor; ridge width w Increasing the capacitance slightly reduces the equivalent capacitance, resulting in a slight increase in the mode frequency. In summary, this T-type dielectric coaxial resonator, by adjusting the blind hole height and ridge width, can effectively push away higher-order modes while independently controlling the fundamental mode frequency, exhibiting superior stopband suppression characteristics. Example

[0024] A fourth-order wide-stopband bandpass filter based on a T-type dielectric coaxial resonator, such as Figure 2 , Figure 3 As shown, the structure consists of four T-type dielectric coaxial resonators DR1, DR2, DR3, and DR4, and three coupling windows 5, 6, and 7. Resonators DR1 and DR2 are connected by coupling window 5, DR2 and DR3 by coupling window 6, and DR3 and DR4 by coupling window 7. The lengths of the three coupling windows are as follows: l cw1 , l cw2 and l cw3Metallized blind vias C1, C2, C3, and C4 are etched at the center of the upper surfaces of resonators DR1, DR2, DR3, and DR4, respectively, to adjust the resonant frequency. Non-metallized rings 1 and 3 are respectively located at the center of the lower surfaces of resonators DR1 and DR4, with feed blind vias 2 and 4 respectively formed at the center of the non-metallized rings 1 and 3, serving as the input and output ports of the filter. The integral dielectric block of this wide stopband bandpass filter is made of sintered ceramic material, and its outer surface, except for the two non-metallized rings 1 and 3, is silver-coated. The height of the feed blind vias 2 and 4 embedded in the dielectric block is adjusted. h p The port coupling strength can be adjusted, thereby enabling the adjustment of the filter's external quality factor. Q e Optimized design.

[0025] The operation of the fourth-order wide-stopband bandpass filter in this embodiment is as follows: the coaxial feed line is connected to feed blind holes 2 and 4 respectively. The input signal is coupled into the resonator DR1 through feed blind hole 2, and the energy transfer between the source and the load is realized through the coupling window 5. The signal then sequentially passes through the resonator DR2, coupling window 6, resonator DR3 and coupling window 7 for interstage coupling and propagation, and is finally output through the resonator DR4 and feed blind hole 4, completing the entire filtering and transmission process.

[0026] This fourth-order wide-stopband bandpass filter based on a T-shaped dielectric coaxial resonator can control the dominant mode frequency by adjusting the heights of the metallized blind holes C1, C2, C3, and C4, and independently adjust the coupling strength between resonators using the coupling window length. Simultaneously, the unique T-shaped dielectric coaxial resonator structure can push harmonic frequencies to a wider frequency band, effectively extending the stopband. Compared to traditional dielectric waveguide filters, this filter significantly improves the stopband width while maintaining low insertion loss and achieving a compact structure.

[0027] A fourth-order wide-stopband bandpass filter based on a T-type dielectric coaxial resonator, its coupling topology and simulation results are as follows: Figure 7 and Figure 8 As shown in the figure. Simulation results show that the filter has a passband of 2480-2650MHz, a center frequency of 2565MHz, a maximum insertion loss of 0.31dB, an operating bandwidth of 170MHz, a relative bandwidth of 6.63%, and a stopband rejection range of over 20dB extending to 7280MHz.

[0028] Figure 9 This demonstrates the coupling coefficient between the resonators. k The curves showing the change in parameters indicate that the coupling between resonators DR1 and DR2, DR2 and DR3, and DR3 and DR4 are achieved through... l cw1 ,l cw2 , l cw3 They are independently adjustable, and their effects on coupling are similar, therefore parameters are defined. l cw To represent the effect of the coupling window length on coupling, as the distance of the coupling window increases... l cw The increase in coupling coefficient k Significantly enhanced. Figure 10 That is the corresponding external quality factor. Q e With the height of the power supply blind hole h p The curve shows a change. It can be seen that the curve changes with the height of the feed blind hole. h p Increasing will Q e The coupling between adjacent resonators decreases. The above results indicate that the coupling between adjacent resonators... k External quality factors Q e Each of these parameters can be independently and effectively controlled.

[0029] The fourth-order wide-stopband bandpass filter designed in this invention, by introducing a T-type dielectric coaxial resonator, achieves miniaturization and enhanced harmonic suppression capability, while also possessing the advantages of wide passband, low insertion loss, and low manufacturing cost, demonstrating good prospects for practical application.

[0030] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A T-type dielectric coaxial resonator, characterized in that, include: The T-shaped cross-section dielectric waveguide has a metallized blind hole at the center of the top surface of the horizontal part, and all outer surfaces of the T-shaped cross-section dielectric waveguide are silver-coated.

2. The T-type dielectric coaxial resonator according to claim 1, characterized in that, The T-section dielectric waveguide is a rectangular dielectric waveguide with a lower half height of [missing information]. h l The waveguide narrows symmetrically inward along its width, forming ridges on both sides with a width of [missing information]. w The T-shaped structure.

3. The T-type dielectric coaxial resonator according to claim 1, characterized in that, The fundamental mode resonant frequency of the T-type dielectric coaxial resonator is determined by the height of the metallized blind via. h r Regulation.

4. The T-type dielectric coaxial resonator according to claim 3, characterized in that, The first higher-order mode frequency of the T-type dielectric coaxial resonator is determined by the width of the ridges on both sides of the T-section dielectric waveguide. w Regulation.

5. A wide stopband bandpass filter based on a T-type dielectric coaxial resonator according to any one of claims 1-4, characterized in that, The filter includes a plurality of T-type dielectric coaxial resonators and a plurality of coupling windows; the plurality of T-type dielectric coaxial resonators are arranged linearly, and adjacent T-type dielectric coaxial resonators are connected by coupling windows located between them to form an integral structure; a feed blind hole is provided at the center of the bottom surface of the vertical part of the T-type dielectric coaxial resonator located at both ends of the integral structure, and a non-metallic ring concentric with the feed blind hole is also provided on the bottom surface.

6. The wide stopband bandpass filter according to claim 5, characterized in that, The dielectric structure of the bandpass filter is a one-piece structure made of sintered ceramic material, and the outer surface of the dielectric structure, except for the non-metallized ring, is covered with silver.

7. The wide stopband bandpass filter according to claim 5, characterized in that, The resonant frequency of the bandpass filter is adjusted by the metallized blind holes of each of the T-type dielectric coaxial resonators.

8. The wide stopband bandpass filter according to claim 5, characterized in that, The coupling strength between adjacent T-type dielectric coaxial resonators is determined by the length of the coupling window. l cw Adjustment, the length of the coupling window l cw The length is the length in the direction perpendicular to the linear arrangement direction.

9. The wide stopband bandpass filter according to claim 5, characterized in that, The quality factor of the bandpass filter Q e Through the height of the power supply blind hole h p adjust.

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