Miniaturized quarter-mode square SIW resonant cavity and bandpass filter
By designing a quarter-mode square SIW resonant cavity and a bandpass filter, and utilizing metal vias and a periodic array structure, the miniaturization and high-frequency loss problems of microwave filters were solved, achieving efficient miniaturization and low-loss performance of the filter.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XINYANG NORMAL UNIVERSITY
- Filing Date
- 2023-04-12
- Publication Date
- 2026-06-05
AI Technical Summary
Existing technologies struggle to miniaturize microwave filters and address the issue of excessive losses at high frequencies, especially in microstrip line structures, and multimode filter research remains relatively niche.
A miniaturized quarter-mode square SIW resonant cavity was designed by setting metal vias and periodic metal via arrays at the vertices of the cavity and forming magnetic walls with 'L'-shaped slots. Different periodic metal via arrays were introduced into the filter to excite three modes.
Significant miniaturization of the filter was achieved, reducing its size and achieving a return loss better than -20dB at 25% relative bandwidth, making it suitable for wireless communication systems.
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Figure CN116315531B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electromagnetic fields and microwave technology, and in particular to a miniaturized quarter-mode square SIW resonant cavity and bandpass filter. Background Technology
[0002] With the rapid development of the communications industry, the low-frequency bands of the radio spectrum are nearing saturation, leading to an increasing demand for exploring high-frequency bands such as microwaves and millimeter waves. A key focus of satellite radar and 5G communication technologies is the development and utilization of microwaves and millimeter waves. The miniaturization and high integration of mobile devices also place increasingly stringent demands on the size of radio frequency (RF) microwave devices. The miniaturization and high power capacity of RF microwave devices are crucial for various engineering design specifications.
[0003] Currently, the design and application of most circuit systems utilize microstrip line technology. Microstrip lines offer advantages such as ease of integration, fabrication, and low cost. However, in the high-frequency range, the open structure of microstrip lines results in excessive losses, failing to meet engineering design specifications. As early as the beginning of the 21st century, Professor Wu Ke of the University of Montreal and Professor Hong Wei of Southeast University, based on their research on the integration problems between planar and non-planar microstrip circuits, proposed the concept of Substrate Integrated Waveguide (SIW). SIW significantly reduces microwave device losses by incorporating a periodic array of metal vias. Unlike the large size of traditional rectangular waveguides, SIW technology offers high Q-values, low losses, simple structures, and ease of integration and miniaturization. Subsequently, Half-mode Substrate Integrated Waveguide (HMSIW) and Quarter-mode Substrate Integrated Waveguide (QMSIW) technologies were proposed, further reducing the size of microwave devices while retaining the original advantages.
[0004] A filter is a frequency selection device that plays an indispensable role in the entire radio frequency circuit. Currently, there is a lot of research on single-mode filters both domestically and internationally, while research on multi-mode filters is relatively niche. However, multi-mode filters are of great significance in the fields of filter miniaturization, ultra-wideband and multi-band design. Summary of the Invention
[0005] To further achieve filter miniaturization, this invention provides a miniaturized quarter-mode square SIW resonant cavity and bandpass filter.
[0006] On one hand, the present invention provides a miniaturized quarter-mode square SIW resonant cavity, comprising: a quarter-mode square SIW cavity, wherein a metal via is disposed at one vertex of the quarter-mode square SIW cavity to form an electric wall, and a periodic array of metal vias is disposed along two adjacent edges of another vertex diagonally opposite to the vertex where the metal via is disposed, and an L-shaped slit is etched on one side of the periodic via array to form a magnetic wall; wherein the quarter-mode square SIW cavity is obtained by cutting a square SIW resonant cavity along mutually perpendicular equivalent magnetic walls.
[0007] Furthermore, the "L"-shaped slit is located on the side of the periodic metal through-hole array near the center of the quarter-mold square SIW cavity.
[0008] On the other hand, the present invention provides a miniaturized quarter-mode square SIW bandpass filter, including a miniaturized quarter-mode square SIW resonant cavity as described above, with the center of the square SIW resonant cavity as the center and a first periodic metal via array arranged along the circumferential direction; four second periodic metal via arrays arranged outside the first periodic metal via array and along the two diagonal directions of the square SIW resonant cavity; and microstrip feed lines arranged on the two adjacent sides where the vertices of the metal vias are located.
[0009] The beneficial effects of this invention are:
[0010] (1) The present invention provides a miniaturized quarter-mode square SIW resonant cavity and a novel miniaturized quarter-mode square SIW three-mode bandpass filter. Compared with traditional SIW-based filters, the present invention uses a quarter-mode square SIW resonant cavity to reduce the size of the filter, and can achieve three modes of excitation by arranging different periodic metal vias at the cavity center, thereby simplifying and miniaturizing the filter design.
[0011] (2) The miniaturized quarter-mode square SIW three-mode bandpass filter of the present invention can achieve a relative bandwidth of 25% and a return loss of better than -20dB at a relative bandwidth of 25% with a harmonic frequency of 4.4GHz. Attached Figure Description
[0012] Figure 1 A schematic diagram of a miniaturized quarter-mode square SIW resonant cavity provided in an embodiment of the present invention;
[0013] Figure 2 A schematic diagram of the structure of a third-order quarter-mode square SIW three-mode bandpass filter provided in an embodiment of the present invention;
[0014] Figure 3 The S-parameter diagram of a third-order quarter-mode square SIW three-mode bandpass filter provided in an embodiment of the present invention. Detailed Implementation
[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0016] Example 1
[0017] like Figure 1 As shown, an embodiment of the present invention provides a quarter-mode square SIW resonant cavity, including a quarter-mode square SIW cavity body. A metal via is provided at one vertex of the quarter-mode square SIW cavity body to form an electric wall. A periodic array of metal vias is provided along the two adjacent edges of the vertex diagonally opposite to the vertex where the metal via is provided. An L-shaped slit is etched on one side of the periodic via array to form a magnetic wall. The quarter-mode square SIW cavity body is obtained by cutting a square SIW resonant cavity along mutually perpendicular equivalent magnetic walls.
[0018] The "L"-shaped slit is located on the side of the periodic metal through-hole array near the center of the quarter-millimeter SIW cavity.
[0019] Among these features, the metal through-holes not only prevent electromagnetic leakage but also improve the quality factor of the resonant cavity. Since the quarter-mode square SIW cavity is formed by cutting a square SIW resonant cavity along vertical and horizontal equivalent magnetic walls, its area is reduced by 75% compared to a traditional square SIW resonant cavity, resulting in a more compact structure suitable for the research and design of miniaturized filters.
[0020] Example 2
[0021] like Figure 2 As shown, this embodiment of the invention provides a miniaturized quarter-mode square SIW bandpass filter, including a miniaturized quarter-mode square SIW resonant cavity as described in the above embodiment. A first periodic metal via array is arranged along the circumference with the center of the square SIW resonant cavity as the center. Four second periodic metal via arrays are arranged outside the first periodic metal via array and along the two diagonal directions of the square SIW resonant cavity. Microstrip feed lines are arranged on the two adjacent sides where the vertices of the metal vias are located.
[0022] A single-cavity tri-mode filter is realized by arranging a first periodic array of metal vias and a second periodic array of metal vias in a quarter-mode square SIW resonant cavity to excite three modes in the cavity. Exciting multiple modes on a single resonator in a single-cavity multi-mode filter can significantly reduce the filter size, which is of great significance for miniaturized filter research. Realizing a single-cavity multi-mode structure based on QMSIW technology can further reduce the filter size. Due to the non-fixed frequency of the multiple modes, tri-mode resonance is achieved, resulting in a 25% relative bandwidth, which improves the filter's signal transmission capability.
[0023] Example 3
[0024] Based on the above embodiments, the single-cavity tri-mode filter provided in this embodiment of the invention comprises a total of three layers: the top and bottom layers are metal plates made of copper, and the middle layer is a dielectric layer made of Taconic RF-5.
[0025] The full-mode square SIW resonant cavity is cut along the vertical and horizontal equivalent magnetic walls, reducing the volume of the full-mode square SIW resonant cavity by 75% to form a quarter-mode square SIW cavity. The quarter-rectangular gaps etched around the perimeter are equivalent to the magnetic walls of the resonant cavity. Periodically arranged metal through holes are set in the cavity. The periodic metal through holes are arranged in a circle and there are periodic metal through holes arranged on the diagonal of the square SIW resonant cavity to realize three excitation control modes.
[0026] Among them, combined Figure 2 As shown, L is the overall length of the second periodic metal via array (also the distance from the intersection of the metal vias arranged diagonally in the cavity to their adjacent edges), Le represents the distance between the microstrip feed line and the vertex where the metal vias are located, W0 is the width of the microstrip feed line, W1 is the width of the quarter-rectangular slit etched around the perimeter, r0 is the radius of each metal via in the via array, r1 represents the radius of the metal via located at the vertex, and r2 represents the radius of the circle formed by the first periodic metal via array. By adjusting the values of L and r2, the frequencies of the three modes can be controlled, exciting the three modes; the width W0 of the microstrip feed line can be roughly obtained from the thickness of the dielectric substrate, the dielectric constant, and the resonant frequency. By adjusting the parameter W0, 50Ω impedance matching can be better achieved.
[0027] As one possible implementation, this single-cavity three-mode bandpass filter uses a thickness h = 0.787 mm and a relative permittivity ε r =2.2, loss tangent tanδ=0.0009 single-layer Taconic RF-5 dielectric substrate.
[0028] Figure 3The S-parameter diagram of this tri-mode bandpass filter is shown. The specifications of this tri-mode bandpass filter are: operating frequency at 4.4 GHz, 3dB relative bandwidth of 25%, in-band insertion loss of -1.5 dB, and return loss in the passband better than -20 dB. The dimensional parameters of the tri-mode bandpass filter are shown in Table 1.
[0029] Table 1. Dimensions of a Tri-mode QMSIW Bandpass Filter (Unit: mm)
[0030] Parameter name L Le <![CDATA[W0]]> <![CDATA[W1]]> <![CDATA[r0]]> numerical values 10 17 0.8 0.35 0.35 Parameter name <![CDATA[r1]]> <![CDATA[r2]]> \ \ \ numerical values 0.4 4 \ \ \
[0031] By employing a quarter-mode structure, the filter achieves miniaturization; the planar dimensions of the bandpass filter, excluding the microstrip feed line, are 30mm*30mm. According to the S-parameter results, the filter operates at 4.4GHz, with a relative bandwidth of 25% at -3dB, an in-band insertion loss of -1.5dB, and a return loss in the passband better than -20dB. Therefore, the tri-mode QMSIW bandpass filter proposed in this embodiment achieves a single-cavity tri-mode structure and meets the corresponding design specifications, showing great promise for application in wireless communication systems.
[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A miniaturized quarter-mode square SIW bandpass filter, characterized in that, The invention includes a miniaturized quarter-mode square SIW resonant cavity. The quarter-mode square SIW resonant cavity comprises a quarter-mode square SIW cavity body. A metal via is disposed at one vertex of the quarter-mode square SIW cavity body to form an electric wall. A periodic array of metal vias is disposed along two adjacent edges containing another vertex diagonally opposite to the vertex containing the metal via. An L-shaped slit is etched on one side of the periodic array of metal vias to form a magnetic wall. The quarter-mode square SIW cavity body is arranged along the two adjacent edges. The square SIW resonant cavity is obtained by cutting a vertical equivalent magnetic wall; the "L"-shaped gap is located on the side of the periodic metal via array near the center of the quarter-modulus square SIW cavity; a first periodic metal via array is arranged along the circumference with the center of the quarter-modulus square SIW resonant cavity as the center; four second periodic metal via arrays are arranged outside the first periodic metal via array and along the two diagonals of the quarter-modulus square SIW resonant cavity; microstrip feed lines are arranged on the two adjacent sides where the vertices of the metal vias are located.