Single-layer multimode SIW dual-passband filter based on through hole perturbation

Abstract

The invention belongs to the technical field of wireless communication, and particularly relates to a single-layer multimode SIW (substrate integrated waveguide) dual-passband filter based on through hole perturbation, which comprises a dielectric substrate and two metal layers respectively positioned on the upper surface and the lower surface of the substrate, first metal through hole arrays are arranged on the periphery of the dielectric substrate. The first metal through hole arrays on the dielectric substrate form a square shape in a surrounding mode, and the square shape, the upper metal layer and the lower metal layer form an SIW square resonant cavity. The left and right symmetrical positions of the upper metal layer and the lower metal layer are respectively provided with an input port and an output port, and the input port and the output port are connected to the SIW square resonant cavity through a 50-ohm microstrip line. According to the invention, a transmission zero point is introduced by disturbing a mode in the SIW square resonant cavity through the metal through holes, so that the filter has high selectivity and better filtering performance; ideal passband center frequency and passband bandwidth can be obtained by adjusting the metal through hole rows in the cavity and the distance between the metal through holes and the center of the resonant cavity.

Description

Technical Field

[0001] The invention belongs to the technical field of wireless communications, and in particular relates to a single-layer multi-mode SIW dual-passband filter based on through-hole perturbation. Background Art

[0002] Wireless communication technology is an important part of the development of modern human society. It plays a huge role in disseminating information, promoting economic and social development, and improving people's work and life. However, the rapid development has brought convenience as well as new difficulties and challenges. The frequency used in communication systems is constantly increasing, and spectrum resources are becoming less and less. Therefore, higher requirements are also put forward for the design of its underlying microwave circuits.

[0003] As an indispensable part of microwave front-end circuits, the main function of microwave filters is to suppress clutter and interference signals in communication systems, select the required frequency band for transmission, and realize frequency selection in communication systems. Its performance affects the performance of the entire communication system. Therefore, the requirements for the function, size and performance of filters are getting higher and higher, and miniaturization, multi-frequency and precision have become the main goals of current filter design.

[0004] Traditional microwave filter design is mainly based on metal waveguide structure and microstrip line structure. Waveguide plays an important role in directional transmission of electromagnetic waves. It is composed of metal shell and internal medium. However, metal waveguide generally has the characteristics of large volume and heavy weight, which is not conducive to integration with other circuit structures in microwave circuits and miniaturization. Later, in order to improve this shortcoming, researchers proposed microstrip structure. Compared with metal waveguide, microstrip circuit has the advantages of small volume, light weight and easy integration, and the problems caused by metal waveguide have been solved. However, with the continuous increase in the frequency of communication system, the problems of high loss and large radiation of microstrip circuit are becoming more and more prominent. In this context, scholars invented the substrate integrated waveguide (SIW) structure. The SIW structure has the advantages of both metal waveguide and microstrip circuit structure, with the characteristics of large quality factor, high power, low loss, small volume, easy integration, etc. At the same time, its structure is simple and can be obtained through printed circuit board (PCB) process or low temperature co-fired ceramic (LTCC) technology, and the cost is low. Therefore, SIW is widely used in the design of various microwave devices, such as filters, antennas, oscillators, couplers and power amplifiers, and the performance of filters has been greatly improved. It is of great help to the miniaturization, multi-frequency and precision of filter design, and has broad development prospects.

[0005] With the rapid development of modern communications, various application systems emerge in an endless stream, spectrum resources are becoming increasingly scarce, and systems are becoming increasingly complex. A system often contains a large number of circuit structures and devices. Therefore, it is hoped that the filter can be miniaturized and multi-frequency while meeting the performance requirements, greatly simplifying the communication system, saving spectrum resources and equipment resources, so that the saved spectrum resources and equipment resources can be used for more applications and systems, and expanding the future development direction of the communication system. Since there are multiple resonant modes in a resonant cavity, general multi-frequency filters often use multiple resonant cavities cascaded in the plane or vertical direction to couple multiple modes to form multi-bands. This method does not take into account the size of the filter.

[0006] In addition, with the development of modern communication systems, applications are becoming more and more complex. A communication system sometimes needs to complete the task of signal transmission in several different frequency bands. Filters working in a single frequency band can no longer meet new communication requirements, and the use of multiple different filters will increase the size and burden of the entire communication system, which is not conducive to the miniaturization and integration of the system.

[0007] Existing dual-passband filters are mostly realized by coupling different modes between multiple resonant cavities. This is a dual-passband filter based on SIW. Its circuit structure is as follows Figure 1 As shown. The circuit consists of two square SIW cavities, two input and output microstrip lines and three layers of metal surfaces. The filter uses the multi-mode response of the square SIW cavity and the coupling effect between SIW cavities to achieve dual-passband filtering performance. By digging a circular groove at the strongest electric field of the middle common metal layer, the electrical coupling of the TE101 mode in the two resonant cavities is achieved. The input and output feeding ends are set on the same side of the upper and lower metal layers to excite the TE102 mode and suppress the TE201 mode. A pair of metal cylindrical through holes are added at the upper and lower symmetrical positions of the circular groove. The center frequency of the first passband is adjusted by adjusting the distance between the through hole and the center of the cavity, thereby achieving the frequency ratio adjustment between the two passbands.

[0008] The existing technical structure requires two complete SIW square cavities, and the two square SIW cavities need to be integrated at the same position up and down, and grooves are dug at the strongest electric field in the center for electrical coupling cascade. The TE101 mode and TE102 mode of the resonant response of the two SIW square cavities are close to each other to generate the first filter passband and the second filter passband respectively. This method requires two SIW resonant cavities to be cascaded vertically up and down, which increases the thickness of the device and is not conducive to miniaturization of the device. At the same time, it is necessary to adjust the electrical coupling coefficient between the resonant cavities, and its structure and design are relatively complex. Summary of the invention

[0009] In order to solve the above technical problems, the present invention proposes a single-layer multi-mode SIW dual-passband filter based on through-hole perturbation, comprising: a dielectric substrate and two metal layers located on the upper and lower surfaces of the substrate, respectively, denoted as upper and lower metal layers;

[0010] The dielectric substrate is provided with a first metal through hole array on all sides, and the first metal through hole array on the dielectric substrate forms a square shape with the upper and lower metal layers to form a SIW square resonant cavity;

[0011] Input and output ports are respectively arranged at left-right symmetrical positions of the upper and lower metal layers, and are connected to the SIW square resonant cavity through a 50-ohm microstrip line.

[0012] Beneficial effects of the present invention:

[0013] The present invention adopts a method of perturbing a square SIW resonant cavity with metal through holes to design a dual-passband filter. The TE101 mode and the TE102 mode in the square SIW resonant cavity are brought close to form a first passband, and the TE201 mode and the TE202 mode are brought close to form a second passband, thereby completing the design of the dual-passband filter. The metal through holes are used to perturb the mode in the SIW square resonant cavity to introduce a transmission zero point, so that the filter has high selectivity and better filtering performance. By adjusting the distance between the metal through holes in the cavity and the metal through holes to the center of the resonant cavity, an ideal passband center frequency and passband bandwidth can be obtained.

[0014] Compared with the existing dual-passband filter design based on substrate integrated waveguide, the present invention can achieve dual-passband filtering performance by only adding metal through holes in a single-layer square resonant cavity to perturb the mode; at the same time, its overall structure is intuitive, small in size, and simple to process, and its simulation results show better frequency selectivity and out-of-band suppression effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the overall structure of the traditional dual-passband filter circuit;

[0016] Figure 2 It is a schematic diagram of the overall structure of a single-layer multi-mode SIW dual-passband filter based on through-hole perturbation of the present invention;

[0017] Figure 3 A top view of a metal layer and a dielectric substrate of a single-layer multi-mode SIW dual-passband filter based on through-hole perturbation according to the present invention;

[0018] Figure 4 A top view of a dielectric substrate and a metal layer of a single-layer multi-mode SIW dual-passband filter based on through-hole perturbation according to the present invention;

[0019] Figure 5A schematic diagram of a SIW square resonant cavity on a dielectric substrate of a single-layer multi-mode SIW dual-passband filter based on through-hole perturbation according to the present invention;

[0020] Figure 6 This is an S-parameter simulation diagram of a single-layer multi-mode SIW dual-passband filter based on through-hole perturbation according to the present invention. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] A single-layer multimode SIW dual-passband filter based on through-hole perturbation, the structure of which is as follows Figure 2 As shown, it includes a dielectric substrate and two metal layers located on the upper and lower surfaces of the substrate respectively. Metal through-hole arrays are arranged around the substrate, and the metal through-hole arrays are arranged in a square shape to construct a SIW square resonant cavity. Metal perturbation through holes and metal through-hole arrays that disturb the resonant mode are arranged at the center and diagonal of the square resonant cavity. The two input and output ports are respectively arranged at the left and right symmetric positions of the upper and lower metal layers, and are connected to the square SIW resonant cavity through a 50-ohm microstrip line.

[0023] Embodiment 1:

[0024] The present invention is composed of only one dielectric substrate and two metal layers (metal layer 1 on the upper surface of the substrate, dielectric substrate 2, and metal layer 3 on the lower surface of the substrate), and the main body is stacked in a 1-2-3 sequence, such as Figure 3 , 4 , as shown in Figure 5.

[0025] The substrate 2 is a complete substrate material, in which a square array of metal through holes 8 is arranged. The upper surface of the metal through hole array 8 is covered with a metal layer 1, and the lower surface is covered with a metal layer 3. A metal through hole 9 is arranged at the center of the substrate, a row of metal through holes 10 is arranged on the main diagonal line of the substrate, and a pair of metal through holes 11 is arranged on the secondary diagonal line of the substrate. 50 ohm microstrip line ports 4 and 6 are arranged on the left side of the metal layer 1 and the right side of the metal layer 3 for subsequent processing and testing, and two 50 ohm microstrip line to SIW coplanar waveguide transition structures 5 and 7 are arranged. At the same time, 4 and 6 are also the input and output ports of the dual-passband filter.

[0026] The metal layer 1, the metal layer 3 and the metal through hole array in the substrate 2 together form a square SIW resonant cavity.

[0027] The input port 4 and the output port 6 are distributed at the symmetrical centers of both sides of the SIW square resonant cavity.

[0028] The working principle of the dual-passband filter is as follows: the input signal is converted from a microstrip TEM mode wave to a TE mode wave through the structure 4 and fed into the filter. The square SIW resonant cavity of the substrate 2 resonates to generate higher-order mode waves such as TE101, TE102, TE201, and TE202. The metal through-hole column 10 and the metal through-hole 11 on the diagonal of the square resonant cavity perturb each mode. The resonant wave is finally output through the output port 6. A single metal through-hole 9 is used to suppress other higher-order modes in the square SIW resonant cavity. The metal through-hole column 10 interferes with the TE101 mode and the TE102 mode in the square SIW resonant cavity, bringing them close to form the first passband. The metal through-hole 11 interferes with the TE201 mode and the TE202 mode in the square SIW resonant cavity, bringing them close to form the second passband. The TE electric field distribution in the square SIW resonant cavity is interfered with, and a transmission zero point is introduced between the first passband and the second passband to achieve higher selectivity. The center frequency of the first passband can be adjusted by the distance between the metal through hole array 10 and the center of the resonant cavity, while the center frequency of the second passband remains basically unchanged, thereby flexibly realizing the frequency ratio of the two passbands. The bandwidth of the first passband and the second passband can be adjusted by the distance between the metal through hole 11 and the center of the resonant cavity, thereby flexibly realizing the bandwidth adjustment of the two passbands.

[0029] In this embodiment, a single-layer multi-mode SIW dual-passband filter structure based on through-hole perturbation of the present invention is simulated, and the simulation results are as follows: Figure 6 As shown, from the simulation results, it can be seen that the first filter passband is 22.39-23.87 GHz, the second filter passband is 26.05-28.81 GHz, the return loss (S11) in the two passbands is better than 24 dB, the insertion loss (S21) is less than 1.1 dB, and the -30 dB stopband suppression can reach 1.82 times the center frequency.

[0030] The single-layer multimode SIW dual-passband filtering structure based on through-hole perturbation proposed in the present invention realizes the dual-passband filtering effect in S parameters, and introduces five transmission zeros in the dual-passband transmission coefficients, which greatly improves the frequency selectivity and out-of-band suppression effect of the dual-passband filter.

[0031] The present invention realizes dual-passband frequency response characteristics by adopting a single-layer square SIW resonant cavity structure, so that the volume of the filter is smaller under the same performance conditions.

[0032] Without changing the side length of the square SIW resonant cavity, the center frequency of the first passband can be adjusted by only changing the position of the metal through-hole column, and the frequency ratio of the two passbands can be flexibly selected.

[0033] There is no need to adjust the coupling coefficient to control the bandwidth, and the bandwidth of the two passbands can be adjusted by simply changing the position of the metal through hole.

[0034] Only by changing the diameter of the central metal through hole, other high-order modes in the square SIW resonant cavity can be suppressed and the filter stopband range can be widened.

[0035] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A single-layer multimode SIW dual-passband filter based on through-hole perturbation, characterized in that: include: A dielectric substrate and two metal layers located on the upper and lower surfaces of the substrate, respectively, denoted as upper and lower metal layers; The dielectric substrate is provided with a first metal through hole array on all sides, and the first metal through hole array on the dielectric substrate forms a square shape with the upper and lower metal layers to form a SIW square resonant cavity; Input and output ports are respectively arranged at left-right symmetrical positions of the upper and lower metal layers, and are connected to the SIW square resonant cavity through a 50-ohm microstrip line.

2. A single-layer multi-mode SIW dual-passband filter based on through-hole perturbation according to claim 1, characterized in that: A metal perturbation through hole is arranged at the center of the SIW square resonant cavity, a second metal through hole array is arranged on its main diagonal, and a pair of third metal through hole arrays are arranged on its secondary diagonal. The metal perturbation through hole, the second metal through hole array and the third metal through hole array are used to perturb the resonant mode.

3. The single-layer multi-mode SIW dual-passband filter based on through-hole perturbation according to claim 1, characterized in that: The peripheries of the input and output ports respectively arranged at the left and right symmetrical positions of the upper and lower metal layers are both provided with a coplanar waveguide transition structure from a 50-ohm microstrip line to a SIW.

4. The single-layer multi-mode SIW dual-passband filter based on through-hole perturbation according to claim 1, characterized in that: The input and output ports are distributed at the symmetrical centers on both sides of the SIW square resonant cavity.

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