Microstrip filter

Abstract

The invention discloses a microstrip filter, and relates to the technical field of passive electronic devices, the microstrip filter comprises a dielectric substrate, a feeder line, a resonance unit, a metal layer and a metal through hole, the feeder line is arranged on the dielectric substrate, and the feeder line comprises an input feeder line and an output feeder line; the resonant unit is arranged on the dielectric substrate, the input feeder line is connected with one end of the resonant unit, the other end of the resonant unit is connected with the output feeder line, the resonant unit comprises a plurality of resonators, the resonators are in coupling connection, each resonator comprises a plurality of edges, and the edges are sequentially connected to form an open ring shape; the metal layer and the dielectric substrate are oppositely arranged and have the same area; the metal through hole is arranged on the resonator and penetrates from the resonator to the metal layer. The microstrip filter provided by the invention has a very good space utilization rate, and various different coupling modes can be generated through different arrangements among the resonators, so that different transmission zeros are generated, and the out-of-band rejection capability of the filter is improved.

Description

Technical Field

[0001] The present application relates to the technical field of passive electronic devices, and in particular to a microstrip filter. Background Art

[0002] With the rapid development of wireless communication technology, microstrip filters, as an indispensable part of RF and microwave communication systems, are mainly used to select signals within a specific frequency range while suppressing unwanted frequency components. They have been widely used in high-tech fields such as wireless communication, radar, WeChat communication, and navigation systems. In microwave circuit systems, the performance of the filter has a great influence on the performance indicators of the circuit, which determines the performance and quality of the entire system. Therefore, in order to improve the performance of wireless communication systems, it is particularly important to study microstrip filters.

[0003] At present, thin-film microstrip filters in related technologies adopt an interdigital structure and a U-shaped structure. However, the traditional microstrip filter has a simple structure, a relative bandwidth range of 5%-60%, and due to the single coupling form and only one transmission zero point, the out-of-band suppression capability at the low-frequency end is poor. Summary of the invention

[0004] The purpose of the present application is to provide a microstrip filter with good space utilization. Different arrangements between resonators can produce a variety of different coupling modes, thereby generating different transmission zeros, thereby improving the out-of-band suppression capability of the filter.

[0005] To achieve the above objectives, this application provides the following solutions:

[0006] In a first aspect, the present application provides a microstrip filter, comprising:

[0007] dielectric substrate;

[0008] A feeder, the feeder being arranged on the dielectric substrate, the feeder comprising an input feeder and an output feeder;

[0009] A resonance unit, wherein the resonance unit is arranged on the dielectric substrate, the input feed line is connected to one end of the resonance unit, and the other end of the resonance unit is connected to the output feed line, the resonance unit comprises a plurality of resonators, each of the resonators is coupled and connected, and each of the resonators comprises a plurality of edges, and the edges are sequentially connected to form an open ring;

[0010] a metal layer, the metal layer being arranged opposite to the dielectric substrate and having the same area as the dielectric substrate;

[0011] A metal through hole is disposed on the resonator and penetrates from the resonator to the metal layer.

[0012] In one embodiment of the present application, the input feed line is connected to the resonator in the resonance unit that is closest to the input feed line, and the output feed line is connected to the resonator in the resonance unit that is closest to the output feed line.

[0013] In one embodiment of the present application, each of the resonators includes a first side and a second side, the through hole is arranged on the first side and located at the intersection of a straight line where the first side is located and a straight line where the second side is located, and the opening is located between the first side and the second side.

[0014] In one embodiment of the present application, when the plurality of sides include three sides, the three sides are equal in length and an angle between straight lines on which two adjacent sides of the three sides are located is 60°.

[0015] In one embodiment of the present application, two first sides of two adjacent resonators among the plurality of resonators are parallel to each other, two openings in two adjacent resonators are both arranged to face away from the center of the dielectric substrate and the two openings are oriented in the same direction; or,

[0016] The two first sides of two adjacent resonators among the plurality of resonators are parallel to each other, and the two openings of the two adjacent resonators are both arranged toward the center of the dielectric substrate; or,

[0017] The first sides of two adjacent resonators of the plurality of resonators are parallel to each other, and one opening of the two adjacent resonators is arranged toward the center of the dielectric substrate, and the other opening is arranged away from the center of the dielectric substrate.

[0018] In one of the embodiments of the present application, there is a coupling gap between two adjacent resonators among the plurality of resonators, and the coupling gap is determined according to a coupling coefficient of the two adjacent resonators, and the coupling coefficient is determined according to a resonant frequency of each resonator among the two adjacent resonators.

[0019] In one embodiment of the present application, the resonant frequency of each of the resonators is a wavelength of a preset coefficient, and the wavelength is determined according to the wavelength corresponding to the center frequency in free space and the effective dielectric constant of the dielectric substrate; the effective dielectric constant of the dielectric substrate is determined according to the relative dielectric constant of the dielectric substrate, the thickness of the dielectric substrate, and the line width of the feed line.

[0020] In one of the embodiments of the present application, the widths of the sides of each of the resonators are equal and are all 0.3 mm.

[0021] In one embodiment of the present application, the dielectric substrate is an alumina ceramic substrate, and the dielectric constant ε of the dielectric substrate isr =9.8, the thickness of the dielectric substrate h=0.254 mm.

[0022] In one of the embodiments of the present application, when the metal through hole is circular, the diameter of the metal through hole is 0.2 mm.

[0023] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0024] The present application provides a microstrip filter, which includes: a dielectric substrate, a feed line, a resonance unit, a metal layer and a metal through hole, wherein the feed line is arranged on the dielectric substrate, the feed line includes an input short line and an output feed line, the resonance unit is arranged on the dielectric substrate, the input feed line is connected to one end of the resonance unit, and the other end of the resonance unit is connected to the output feed line, the resonance unit includes a plurality of resonators, each resonator is coupled and connected, each resonator includes a plurality of edges and each edge is connected in sequence to form an open ring; the metal layer is arranged opposite to the dielectric substrate and has the same area; the metal through hole is arranged on the resonator and penetrates from the resonator to the metal layer. Compared with the prior art, the microstrip filter of the present application can provide physical support for the entire microstrip filter due to the provision of a dielectric substrate, ensure that components such as a feed line and a resonance unit are stably fixed on its surface, and provide a metal layer as a ground plane to provide a stable reference potential for the feed line and the resonance unit. The external input signal is transmitted to the resonance unit through the feed line, which is convenient for the resonator to trigger the resonance process and realize the filtering function, and the normal transmission of the signal in the structure is ensured by providing a metal through hole; and because the resonator is provided with multiple sides and the sides are connected in sequence to form an open ring, it has a good space utilization rate, and different arrangements between the resonators can produce a variety of different coupling modes, thereby producing different transmission zero points, which greatly improves the out-of-band suppression capability of the filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 A schematic diagram of the structure of a microstrip filter provided in one embodiment of the present application;

[0027] Figure 2 A schematic diagram of a top view of a microstrip filter provided in an embodiment of the present application;

[0028] Figure 3A structural diagram of a first coupling mode provided in an embodiment of the present application;

[0029] Figure 4 A structural diagram of a first coupling mode provided in an embodiment of the present application;

[0030] Figure 5 A schematic diagram of the structure of a third coupling mode provided in an embodiment of the present application;

[0031] Figure 6 A schematic diagram of S-parameter simulation results provided in an embodiment of the present application;

[0032] Description of reference numerals:

[0033] Dielectric substrate-10, feeding line-20, resonance unit-30, resonator-31, metal layer-40, metal through hole-50, first side-311, second side-312, opening-313, coupling gap-314. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0035] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0036] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0038] In the description of this embodiment, the terms "upper", "lower", "left", "right" and other directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0039] As mentioned in the background technology, in the process of rapid development of wireless communication technology and electronic equipment, miniaturized and high-performance electronic devices have become the main development direction in the microwave radio frequency field. Filters, as vital passive electronic devices in communication systems, can achieve the passage of specified signals and filtering of interference signals. At present, the thin film microstrip filter of the related technology adopts an interdigital structure. However, the traditional interdigital microstrip filter has a simple structure, a relative bandwidth range of 5%-60%, and due to the single coupling form and only one transmission zero point, the low-frequency end out-of-band suppression capability is poor.

[0040] Based on the above-mentioned defects, an embodiment of the present application provides a microstrip filter. Compared with the prior art, the microstrip filter of the present application can provide physical support for the entire microstrip filter due to the provision of a dielectric substrate, ensure that components such as a feed line and a resonance unit are stably fixed on its surface, and provide a metal layer and a metal through-hole. The metal layer is used as a ground plane to provide a stable reference potential for the feed line and the resonance unit, and transmit the external input signal to the resonance unit through the feed line, so that the resonator triggers the resonance process and realizes the filtering function, and ensures the normal transmission of the signal in the structure by providing a metal through-hole; and because the resonator is provided with multiple edges and the edges are connected in sequence to form an open ring, it has a good space utilization rate, and different arrangements between the resonators can produce a variety of different coupling modes, thereby producing different transmission zero points, which greatly improves the out-of-band suppression capability of the filter.

[0041] See also Figure 1As shown, the microstrip filter comprises: a dielectric substrate 10, a feed line 20, a resonance unit 30, a metal layer 40 and a metal through hole 50. The feed line 20 is arranged on the dielectric substrate 10, and the feed line 20 comprises an input feed line and an output feed line; the resonance unit 30 is arranged on the dielectric substrate, the input feed line is connected to one end of the resonance unit 30, and the other end of the resonance unit 30 is connected to the output feed line. The resonance unit 30 comprises a plurality of resonators 31, and each resonator 31 is coupled and connected to each other, and each resonator 31 comprises a plurality of edges, and each edge is sequentially connected to form an opening 313 ring shape; the metal layer 40 is arranged opposite to the dielectric substrate and has the same area; the metal through hole 50 is arranged on the resonator 31 and passes through the resonator 31 to the metal layer 40.

[0042] It should be noted that the dielectric substrate 10 serves as a physical support, so that the feed line 20, the resonant unit 30 and other components maintain a stable relative position and are stably fixed on its surface. The dielectric properties of the dielectric substrate 10 will affect the electromagnetic field distribution. The dielectric substrates 10 with different dielectric constants can change the wavelength of the electromagnetic wave, realize circuit miniaturization, and play an isolation role to prevent short circuits of circuit components in different layers and ensure that the current flows along the designed path. In the process of manufacturing the microstrip filter, the feed line 20 and the resonant unit 30 can be attached to the dielectric substrate 10 through processes such as photolithography and etching.

[0043] The feeder 20 is used to transmit an externally input RF signal to the resonance unit 30, so that the resonance unit 30 resonates under the excitation of the input signal. The input RF signal may be sent by a signal source, and the length and width of the feeder 20 may affect the characteristic impedance. By adjusting the geometric parameters such as the length and width of the feeder 20, the characteristic impedance can be controlled to achieve matching with the output impedance of the signal source and the input impedance of the load, reduce signal reflection, and improve transmission efficiency.

[0044] It is understandable that the feed line 20 effectively excites the signal energy into the resonance unit 30. When the signal is transmitted to the resonance unit 30, it will cause a change in the electromagnetic field inside the resonator 31, thereby triggering the resonance process. For example, if the frequency of the signal transmitted by the feed line 20 is close to the resonance frequency of the resonance unit 30, the resonator 31 in the resonance unit 30 will produce a strong resonance, and the signal of the frequency will be amplified and selected. The feed line 20 can be a microstrip line. For example, the feed line 20 in the present application can be composed of a 50Ω microstrip line.

[0045] The above-mentioned resonance unit 30 is a core component of the filtering function, has a resonance function, can store and release electromagnetic energy at a specific frequency, and has a strong response to the frequency signal. It can be used for filtering, allowing signals near the resonance frequency to pass through and suppressing signals of other frequencies. By adjusting the geometric dimensions in the resonator 31 to change the resonance frequency, frequency selection can be achieved to meet the selection requirements of specific frequency band signals in fields such as wireless communications. The above-mentioned resonance unit 30 includes a plurality of resonators 31, and the resonator 31 has a specific resonance frequency. When the signal frequency transmitted by the feeder 20 is consistent with the resonance frequency, the electric field and magnetic field inside the resonator 31 will resonate to store and release electromagnetic energy.

[0046] The resonator 31 in the resonance unit 30 and other adjacent resonators 31 or feeder 20 affect each other through electromagnetic coupling, and this coupling mode can be electric field coupling, magnetic field coupling, or both. By controlling the coupling strength, the bandwidth and in-band characteristics of the filter can be adjusted. For example, increasing the coupling strength will widen the bandwidth of the filter.

[0047] Optionally, the resonance unit 30 includes a plurality of resonators 31, each of which includes a plurality of sides and each side is sequentially connected to form a ring, the ring including an opening 313, and the plurality of sides may be three sides, four sides, or five sides, that is, it is presented as an open triangular ring, an open quadrangular ring, an open pentagonal ring, etc. The resonators 31 are coupled and connected with each other, and have a variety of arrangement modes, which will produce different coupling modes, thereby producing different transmission zero points, thereby improving the out-of-band suppression capability of the filter. The more sides the resonator 31 has, the weaker the coupling capability between the two resonators 31, and the lower and narrower the relative bandwidth range. Preferably, the resonator 31 can be set to a triangular ring structure with an opening 313, which not only ensures the coupling capability, but also produces different coupling modes, thereby improving the diversity of the product.

[0048] The metal layer 40 acts as a ground plane, providing a stable reference potential for the feed line 20 and the resonant unit 30, thereby ensuring the normal operation of the microstrip filter. It can also act as an electromagnetic shielding layer to reflect and absorb external electromagnetic interference, prevent internal electromagnetic signals from radiating outward, and reduce electromagnetic compatibility issues. The metal layer 40 is arranged on the back of the dielectric substrate, and cooperates with the resonator 31 to affect the electromagnetic field distribution around the resonator 31. The existence of the metal layer 40 changes its boundary conditions, so that the electromagnetic field is reflected back and forth between the resonator 31 and the ground plane, thereby helping to form a stable resonance mode.

[0049] The metal layer 40 can be used as an electromagnetic shielding layer to prevent external electromagnetic interference from entering the microstrip filter, and also prevent the internal signal from radiating outward, which helps to maintain the stability of the filter performance and reduce the impact of external interference on the filtering effect. For example, in a complex electromagnetic environment, such as when multiple wireless devices are working at the same time, the metal layer 40 on the back can effectively shield the electromagnetic waves emitted by other devices, ensuring that the microstrip filter only filters the designed frequency.

[0050] In the microstrip filter, the metal through hole 50 is used to connect circuit elements of different layers. For example, one end of the metal through hole 50 is connected to the ground end of the resonator 31, and the other end is connected to the metal layer 40 of the dielectric substrate. It can realize the electrical connection between different layers, connect the front circuit elements with the metal layer 40 or other signal layers grounded on the back, and ensure the normal transmission of signals in the multi-layer structure. As an electromagnetic transmission channel, it provides a low-loss transmission path for electromagnetic signals between different layers in high-speed digital circuits or high-frequency analog circuits, reducing signal attenuation and distortion.

[0051] The input feeder is connected to the resonator 31 in the resonance unit 30 that is closest to the input feeder, and the output feeder is connected to the resonator 31 in the resonance unit 30 that is closest to the output feeder.

[0052] It should be noted that, taking the above-mentioned dielectric substrate as a rectangle as an example, the resonators 31 are arranged in sequence along the length of the rectangle, taking the input feeder as the leftmost feeder 20 and the output feeder as the rightmost feeder 20 as an example, the resonator 31 closest to the input feeder is the leftmost resonator 31 among all the resonators 31, and the resonator 31 closest to the output feeder is the rightmost resonator 31 among all the resonators 31. The above-mentioned input feeder is connected to the leftmost resonator 31 among all the resonators 31, and the output feeder is connected to the rightmost resonator 31 among all the resonators 31.

[0053] The working principle of the microstrip filter is to utilize the feed line 20 and the resonant unit 30 to generate different responses to signals of different frequencies, thereby achieving a filtering function.

[0054] In this embodiment, by connecting the input feed line and the resonator 31 in the resonance unit 30 that is closest to the input feed line, and connecting the output feed line and the resonator 31 in the resonance unit 30 that is closest to the output feed line, the signal can be effectively transmitted to the resonator 31, thereby improving the signal transmission efficiency.

[0055] The present application provides a microstrip filter, which includes: a dielectric substrate 10, a feed line 20, a resonance unit 30, a metal layer 40 and a metal through hole 50, wherein the feed line 20 is arranged on the dielectric substrate 10, the feed line 20 includes an input feed line and an output feed line, the resonance unit 30 is arranged on the dielectric substrate 10, the input feed line 20 is connected to one end of the resonance unit 30, and the other end of the resonance unit 30 is connected to the output feed line, the resonance unit 30 includes a plurality of resonators 31, each resonator 31 is coupled and connected, each resonator 31 includes a plurality of edges and each edge is connected in sequence to form an opening 313 ring; the metal layer 40 is arranged opposite to the dielectric substrate and has the same area; the metal through hole 50 is arranged on the resonator 31 and passes through the resonator 31 to the metal layer 40. Compared with the prior art, the microstrip filter of the present application is provided with a dielectric substrate 10, which can provide physical support for the entire microstrip filter, ensure that components such as the feed line 20 and the resonance unit 30 are stably fixed on its surface, and provide a metal layer 40 and a metal through hole 50, and use the metal layer 40 as a ground plane to provide a stable reference potential for the feed line 20 and the resonance unit 30, and transmit the external input signal to the resonance unit 30 through the feed line 20, so that the resonator 31 triggers the resonance process and realizes the filtering function, and ensures the normal transmission of the signal in the structure by setting the metal through hole; and because the resonator 31 is provided with multiple edges and the edges are connected in sequence to form an open ring 313, it has a good space utilization rate, and different arrangements between the resonators 31 can produce a variety of different coupling modes, thereby generating different transmission zero points, which greatly improves the out-of-band suppression capability of the filter.

[0056] In one embodiment, see Figure 2 As shown, each resonator 31 includes a first side 311 and a second side 312 , the through hole is arranged on the first side 311 and located at the intersection of the straight line where the first side 311 is located and the straight line where the second side 312 is located, and the opening 313 is located between the first side 311 and the second side 312 .

[0057] In this embodiment, the resonator 31 may include three sides, that is, a three-sided ring with an opening 313, which includes a first side 311 and a second side 312, and may also include other sides. The widths of the first side 311 and the second side 312 may be equal or unequal. When the widths of the first side 311 and the second side 312 are equal, their widths may both be 0.3 mm. The lengths of the three sides may be equal or unequal.

[0058] It is understandable that by adjusting the geometric parameters of the resonator 31, such as the length of the side and the size of the opening 313, the resonant frequency can be changed, thereby selecting the frequency range to be filtered. For example, increasing the length of the three sides will reduce the resonant frequency, and reducing the size of the opening 313 will increase the resonant frequency.

[0059] The above-mentioned metal through hole 50 can be a circular hole, a square hole, a triangular hole, etc., as long as it can guide the signal to be transmitted between different layers. In this embodiment, there is no limitation on the shape of the metal through hole 50. When the metal through hole 50 is a circular hole, the diameter of the metal through hole 50 is smaller than the width of the side, and the resonator 31 is connected to the metal layer 40 on the back through the metal circular hole. Among them, when the metal through hole 50 is circular, the diameter of the metal through hole 50 is 0.2mm. In the design of the microstrip filter, the performance of the filter can be optimized by changing the parameters such as the position, size and number of the metal through hole 50. For example, by reasonably arranging the metal through holes 50, the coupling between different layers is enhanced or weakened, thereby changing the frequency response characteristics of the filter.

[0060] See also Figure 2 As shown, when the above-mentioned multiple edges include three edges, the angle between the straight lines where two adjacent edges of the three edges are located is 60°, which can be understood as the ring formed by the three edges is a triangular ring. By setting the angles of the three corners of the opening 313 triangular ring composed of three edges to 60°, due to the uniqueness of its structure, it can have better directional selectivity in the setting of the microstrip filter, thereby effectively reducing the size of the microstrip filter and meeting the needs of miniaturization in modern communication technology.

[0061] In this embodiment, the resonator 31 is set to have three sides with equal length and width, but with different settings on the three sides, so that there are multiple arrangements between two adjacent resonators 31, which will produce different couplings, and then produce different transmission zeros, thereby improving the out-of-band suppression capability of the microstrip filter, and solving the problem that the out-of-band suppression capability of the traditional filter is poor and the out-of-band suppression curve trend is single. At the same time, the resonator 31 is set to an opening 313 triangular ring resonator 31, and this structure has good space utilization and can effectively reduce the size of the microstrip filter.

[0062] In one embodiment, the two first sides 311 of two adjacent resonators 31 among the plurality of resonators 31 are parallel to each other, the two openings 313 are both arranged to face away from the center of the dielectric substrate 10, and the two openings 313 are in the same direction; or, the two first sides 311 of two adjacent resonators 31 among the plurality of resonators 31 are parallel to each other, and the two openings 313 of the two adjacent resonators 31 are both arranged to face the center of the dielectric substrate 10; or, the first sides 311 of two adjacent resonators 31 among the plurality of resonators are parallel to each other, and one of the openings 313 of the two adjacent resonators 31 is arranged to face the center of the dielectric substrate 10, and the other opening 313 is arranged to face away from the center of the dielectric substrate 10.

[0063] It should be noted that the resonance unit 30 includes a plurality of resonators 31, and there may be a plurality of arrangements between two adjacent resonators 31 in the plurality of resonators 31, and each arrangement may produce a different coupling connection. The structures of the resonators 31 may be the same, for example, they are all triangular ring structures including an opening 313. The resonant frequency of the resonator 31 is a quarter wavelength.

[0064] As a possible implementation, see Figure 3 As shown, the above figure shows the arrangement between two adjacent resonators 31 in the plurality of resonators 31, and the two resonators 31 each include a first side 311, a second side 312, an opening 313 and a metal through hole 50. The dielectric substrate 10 may include a long side and a wide side, and the first side 311 is provided with a metal through hole 50, and an opening 313 is provided between the first side 311 and the second side 312. The two first sides 311 of the two adjacent resonators 31 in the plurality of resonators 31 are parallel to each other, which can be understood as the two first sides 311 are arranged in parallel along the wide side of the dielectric substrate 10 and the parallel lines are perpendicular to the long side of the dielectric substrate 10, the two openings 313 are arranged away from the center of the dielectric substrate 10 and the two openings 313 are oriented toward the long side of the dielectric substrate 10, or the two first sides are arranged in parallel along the long side of the dielectric substrate 10 and the parallel lines are perpendicular to the wide side of the dielectric substrate 10, the two openings 313 are arranged away from the center of the dielectric substrate 10 and the two openings 313 are oriented toward the wide side of the dielectric substrate 10.

[0065] As another possible implementation, see Figure 4 As shown, a metal through hole 50 is provided on the first side 311 of the two adjacent resonators 31, an opening 313 is provided between the second side 312 and the first side 311, the two first sides 311 of the two adjacent resonators 31 are parallel to each other, and the two openings 313 are both arranged toward the center of the dielectric substrate 10. It can be understood that the opening directions of the two openings 313 are parallel to each other, and they can be both arranged along the long side of the dielectric substrate 10, and can also be both arranged along the wide side of the dielectric substrate 10.

[0066] As another possible implementation, see Figure 5 As shown, the first sides 311 of the two adjacent resonators 31 are provided with a metal through hole 50, an opening 313 is provided between the second side 312 and the first side 311, the two first sides 311 of the two adjacent resonators 31 are parallel to each other, one of the two openings 313 is arranged toward the center of the dielectric substrate 10, and the other opening 313 is arranged away from the center of the dielectric substrate 10, which means that one of the openings 313 is arranged toward the center of the dielectric substrate 10, and the other opening 313 is arranged along the wide side of the dielectric substrate 10, or one of the openings 313 is arranged toward the center of the dielectric substrate 10, and the other opening 313 is arranged along the long side of the dielectric substrate 10.

[0067] It can be understood that the opening 313 facing the center of the dielectric substrate 10 may be the central axis of the dielectric substrate 10 , the center line of the dielectric substrate 10 , or the center point of the dielectric substrate 10 .

[0068] In this embodiment, by arranging two adjacent resonators 31 in the resonators 31 and not limited to the above-mentioned multiple arrangements, the two resonators can have different coupling characteristics, thereby generating different transmission zeros, which greatly improves the out-of-band suppression capability of the filter.

[0069] In one embodiment, a coupling gap 314 exists between two adjacent resonators 31 among the plurality of resonators 31 . The coupling gap 314 is determined according to a coupling coefficient between the two adjacent resonators 31 . The coupling coefficient is determined according to a resonant frequency of each resonator 31 among the two adjacent resonators 31 .

[0070] It should be noted that there is a coupling gap 314 between two adjacent resonators 31. In the process of designing the microstrip filter, the resonant frequencies of the two adjacent resonators 31 are obtained, and the coupling coefficient of the two resonators 31 is determined according to the resonant frequencies, and then the coupling gap 314 is determined according to the coupling coefficient. The resonant frequency of each resonator 31 in the two adjacent resonators 31 can be obtained through simulation, for example, f1 and f2 respectively, and then the coupling coefficient K is calculated by the following formula: ij :

[0071]

[0072] Wherein, f1 and f2 are both the resonance frequencies of the two resonators 31 .

[0073] The resonant frequency of the resonator 31 can be 15 GHz. The microstrip filter in the embodiment of the present application can be applied to a wireless communication system, and its operating bandwidth can be 14.5-15.5 GHz, the center frequency is 15 GHz, and the relative bandwidth is about 6.6%. By using the above Figure 3 , Figure 4 and Figure 5 The coupling mode is used, and the simulation software is used to simulate it to obtain the S parameter simulation curve, which can be seen in Figure 6 The schematic diagram of the S parameter simulation curve provided in the embodiment of the present application shows that the coupling mode generated by the arrangement of the resonator 31 provided in the present embodiment has two transmission zeros at the high frequency end and good out-of-band suppression at the low frequency end. In the present embodiment, the transmission zero can be increased by changing the arrangement mode, and the resonator 31 of this structure has high suppression and the S curve can be changed according to the different couplings.

[0074] Among them, the intensity and mode of coupling between the two resonators 31 will affect the frequency response characteristics of the microstrip filter. By adjusting the coupling coefficient, the bandwidth and other characteristics of the filter can be controlled. The microstrip filter with opening 313 triangular rings provided in this embodiment has a coupling coefficient between two opening 313 triangular rings with different arrangements of about 0.1 to 0.2, and a relative bandwidth range of 3% to 20%, while the relative bandwidth range of the traditional interdigital filter is 5% to 60%. When the filter is narrowband, the opening 313 triangular ring microstrip filter has a smaller coupling gap 314 width and a smaller size than the traditional interdigital filter.

[0075] In one embodiment, the resonant frequency of each resonator 31 is a wavelength of a preset coefficient, and the wavelength is determined according to the wavelength corresponding to the center frequency in free space and the effective dielectric constant of the dielectric substrate; the effective dielectric constant of the dielectric substrate is determined according to the relative dielectric constant of the dielectric substrate, the thickness of the dielectric substrate, and the line width of the feed line 20.

[0076] It should be noted that the above-mentioned preset coefficient can be customized according to actual needs, for example, it can be 1 / 4. Different dielectric substrates and geometric parameters of the feed line 20 affect the performance of the microstrip filter and also affect the resonant frequency. In the process of designing the microstrip filter, the resonant frequency can be determined first, and then the effective dielectric constant of the dielectric substrate is determined according to the wavelength corresponding to the center frequency in free space and the wavelength of the preset coefficient, and the thickness of the dielectric substrate and the line width of the feed line 20 are determined according to the effective dielectric constant.

[0077] Exemplarily, when the resonator 31 is an open triangular ring resonator 31, both are λ g / 4 resonator 31, wavelength Where λ0 is the wavelength corresponding to the center frequency in free space, ε re is the effective dielectric constant of the dielectric substrate.

[0078] The effective dielectric constant of the above dielectric substrate can be expressed by the following formula:

[0079]

[0080] Where, h is the thickness of the dielectric substrate, w is the line width of the feed line 20, ε r is the relative dielectric constant of the dielectric substrate.

[0081] The resonator 31 has a specific resonant frequency. When the frequency of the input signal matches the resonant frequency of the resonator 31, the resonator 31 will resonate and produce a strong response to the signal of the frequency, such as increasing the amplitude of the signal or changing the phase of the signal, while the response to signals of other frequencies is weak or no response. In this embodiment, by reasonably designing the size, shape and structural parameters of the resonator 31, its resonant frequency can be adjusted, thereby realizing the selection of a specific frequency signal and further realizing the filtering function.

[0082] It is understandable that the feed line 20 can be a microstrip line. A microstrip line is a transmission line whose geometric shape and size determine its transmission characteristics for signals of different frequencies. When a signal is transmitted on a microstrip line, signals of different frequencies will have different phase velocities and attenuation constants. When a high-frequency signal is transmitted on a microstrip line, due to factors such as the skin effect, a large attenuation will occur, while a low-frequency signal will have a relatively small attenuation. This characteristic enables the microstrip line itself to have a certain screening effect on signals of different frequencies.

[0083] In this embodiment, by setting the resonant frequency of each resonator 31 to a wavelength of a preset coefficient, the thickness of the dielectric substrate and the line width of the feed line 20 can be flexibly set, so that a variety of coupling arrangements are formed between the resonators 31, solving the problem of poor out-of-band suppression capability and a single out-of-band suppression curve trend of traditional filters.

[0084] In one embodiment, the dielectric substrate is an alumina ceramic substrate, and the dielectric constant ε r =9.8, the thickness of the dielectric substrate h = 0.254 mm.

[0085] In this embodiment, since alumina ceramics have a relatively high dielectric constant, it helps to reduce the physical size of the transmission line, thereby making the circuit more compact. Alumina ceramics have low loss characteristics and excellent thermal conductivity. The thickness of the dielectric substrate is set to 0.254 mm, which can optimize impedance matching. For devices such as filters that rely on a specific resonant frequency to work, the substrate thickness will change the effective propagation path of the electromagnetic wave, thereby affecting the final resonant frequency point. Therefore, by setting a dielectric substrate of this structure, the stability and controllability of the filter are improved while meeting specific electrical performance requirements.

[0086] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0087] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A microstrip filter, characterized in that: The microstrip filter comprises: dielectric substrate; A feeder, the feeder being arranged on the dielectric substrate, the feeder comprising an input feeder and an output feeder; A resonance unit, wherein the resonance unit is arranged on the dielectric substrate, the input feed line is connected to one end of the resonance unit, and the other end of the resonance unit is connected to the output feed line, the resonance unit comprises a plurality of resonators, each of the resonators is coupled and connected, and each of the resonators comprises a plurality of edges, and the edges are sequentially connected to form an open ring; a metal layer, the metal layer being arranged opposite to the dielectric substrate and having the same area as the dielectric substrate; A metal through hole is disposed on the resonator and penetrates from the resonator to the metal layer.

2. The microstrip filter according to claim 1, characterized in that: The input feed line is connected to a resonator in the resonance unit that is closest to the input feed line, and the output feed line is connected to a resonator in the resonance unit that is closest to the output feed line.

3. The microstrip filter according to claim 1, characterized in that: Each of the resonators includes a first side and a second side, the through hole is arranged on the first side and located at the intersection of a straight line where the first side is located and a straight line where the second side is located, and the opening is located between the first side and the second side.

4. The microstrip filter according to claim 3, characterized in that: When the plurality of sides include three sides, the angle between the straight lines on which two adjacent sides of the three sides are located is 60°.

5. The microstrip filter according to claim 3, characterized in that: Two first sides of two adjacent resonators among the plurality of resonators are parallel to each other, and two openings in two adjacent resonators are both arranged to face away from the center of the dielectric substrate and the two openings are oriented in the same direction; or, The two first sides of two adjacent resonators among the plurality of resonators are parallel to each other, and the two openings of the two adjacent resonators are both arranged toward the center of the dielectric substrate; or, The first sides of two adjacent resonators of the plurality of resonators are parallel to each other, and one opening of the two adjacent resonators is arranged toward the center of the dielectric substrate, and the other opening is arranged away from the center of the dielectric substrate.

6. The microstrip filter according to claim 1, characterized in that: There is a coupling gap between two adjacent resonators among the plurality of resonators, and the coupling gap is determined according to a coupling coefficient between the two adjacent resonators, and the coupling coefficient is determined according to a resonant frequency of each resonator among the two adjacent resonators.

7. The microstrip filter according to claim 1, characterized in that: The resonant frequency of each resonator is a wavelength of a preset coefficient, and the wavelength is determined according to the wavelength corresponding to the center frequency in free space and the effective dielectric constant of the dielectric substrate; the effective dielectric constant of the dielectric substrate is determined according to the relative dielectric constant of the dielectric substrate, the thickness of the dielectric substrate, and the line width of the feed line.

8. The microstrip filter according to claim 6, characterized in that: The widths of the sides of each resonator are equal and are all 0.3 mm.

9. The microstrip filter according to claim 1, characterized in that: The dielectric substrate is an alumina ceramic substrate, and the dielectric constant ε r =9.8, the thickness of the dielectric substrate h=0.254 mm.

10. The microstrip filter according to claim 1, characterized in that: When the metal through hole is circular, the diameter of the metal through hole is 0.2 mm.

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