Coaxial double-stop-band filter

Abstract

The invention belongs to the technical field of microwave communication, and relates to a coaxial double-stop-band filter, which comprises an inner conductor, an outer conductor, an insulating medium body, a signal input port and a signal output port, and is characterized in that the inner conductor is coaxially sleeved in the outer conductor, and the insulating medium body is positioned between the inner conductor and the outer conductor; two ends of the inner conductor are respectively connected with signal connecting ends of the signal input port and the signal output port; the outer conductor comprises a metal cylinder, the two ends of the metal cylinder are fixedly connected with the signal input port and the signal output port respectively, two defected ground structures which are symmetrically distributed relative to the central plane of the outer conductor are arranged on the metal cylinder, and each defected ground structure comprises a first gap and three second gaps which are arranged in parallel at intervals. The length direction of the second gaps is parallel to the axial direction of the metal cylinder, and the three second gaps are communicated through the first gap. The dual-band interference suppression performance is excellent, the passband insertion loss is low, the structure is novel, the power capacity is large, and processing is easy.

Description

Technical Field

[0001] This invention belongs to the field of microwave communication technology, and specifically relates to a coaxial dual stopband filter. Background Technology

[0002] Band-stop filters, as one of the key components of wireless communication systems, can filter out unwanted in-band signals. In recent years, dual-stopband filters have been widely used in multi-band wireless communication systems because they can suppress interference on two frequency bands simultaneously. Compared with traditional cascaded single-band stopband filters, dual-stopband filters are not only smaller and cheaper to manufacture, but also have lower in-passband insertion loss and better performance. On the other hand, as communication systems increasingly adopt centimeter-wave and millimeter-wave frequency bands, the disadvantages of microstrip filters, such as low power capacity, high insertion loss, and large size, become apparent. In contrast, coaxial filters, due to their high power handling capacity, low in-band insertion loss, and ease of fabrication, are widely used in airborne equipment, satellite communications, radar, and other systems.

[0003] However, currently, realizing dual stopband filtering requires multiple single-band coaxial stopband filters to be cascaded, which results in the entire filtering unit being bulky, complex in structure, and difficult to manufacture. Based on the rapid development of wireless communication technology and the demand for compactness, the development of high-performance coaxial dual stopband filters has become urgent. Summary of the Invention

[0004] In view of this, the present invention provides a coaxial dual stopband filter, which solves the problems in the prior art.

[0005] The technical solution of this invention is: A coaxial dual-stopband filter includes an inner conductor, an outer conductor, an insulating dielectric, a signal input port, and a signal output port. The inner conductor is coaxially fitted inside the outer conductor, and the insulating dielectric is located between the inner and outer conductors. The two ends of the inner conductor are respectively connected to the signal connection ends of the signal input port and the signal output port. The outer conductor includes a metal cylinder whose two ends are fixedly connected to the signal input port and the signal output port, respectively. Two defect ground structures are provided on the metal cylinder, symmetrically distributed with respect to the central plane of the outer conductor. The defect ground structure includes a first gap and three parallel and spaced second gaps. The length direction of the second gaps is parallel to the axial direction of the metal cylinder, and the three second gaps are connected through the first gaps.

[0006] Preferably, the insulating medium is polytetrafluoroethylene or air.

[0007] Preferably, both the inner and outer conductors are made of pure copper, corresponding to copper with a copper content of ≥99.9% that has good electrical and thermal conductivity in actual production.

[0008] Preferably, the length ratio of the first slot to the second slot is 22:1, and the height ratio of the first slot to the second slot is 1:22.

[0009] Preferably, the first slot is located at the middle position of the second slot.

[0010] Preferably, the second slot is arranged in the center of the metal cylinder.

[0011] Preferably, the signal input port includes a first flange and a first adapter arranged in the middle of the first flange. The first flange is fixedly connected to one end of the metal cylinder, and the first adapter is connected to one end of the inner conductor.

[0012] Preferably, the signal output port includes a second flange and a second adapter arranged in the middle of the second flange. The second flange is fixedly connected to the other end of the metal cylinder, and the second adapter is connected to the other end of the inner conductor.

[0013] Preferably, according to different connection objects, the first adapter and the second adapter are one of coaxial SMA connectors, BNC connectors or TNC connectors.

[0014] Compared with the prior art, a coaxial dual-stopband filter provided by the present invention has an overall coaxial cylindrical structure. From the inside to the outside, it includes an inner conductor, an insulating dielectric body, and an outer conductor with an etched defected ground structure. Two "king" - shaped defected ground structures rotated 90 degrees are etched on the outer conductor. This defected ground structure can change the current distribution of the metal structure, increase the distributed capacitance of the coaxial dual-stopband filter, introduce new resonant frequency points, increase the number of stopbands, and achieve the dual-stopband filtering function. While retaining the characteristic of large power capacity of the coaxial structure, it greatly broadens the stopband suppression bandwidth, and can achieve dual-stopband filtering without cascading multiple filters, saving costs and space. At the same time, since the defected ground structure of this coaxial dual-stopband filter is located in the outer conductor layer, the structural improvement can be achieved only by etching on the basis of the original coaxial structure without adding new physical structures. Such a design not only reduces the volume of the entire coaxial dual-stopband filter, but also has a simple structure and is easy to process and implement.

[0015] The present invention combines the design concept of the coaxial dual-stopband filter with the defected ground structure, making the coaxial dual-stopband filter have excellent dual-band interference suppression performance, low passband insertion loss, and characteristics of novel structure, large power capacity, and easy processing. It can be widely applied in the field of microwave communication, has strong practicability, and is worthy of promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is the overall structure diagram of the present invention.

[0017] Figure 2 This is the front view of the present invention.

[0018] Figure 3 This is a graph of the S-parameters of the present invention.

[0019] Explanation of reference numerals in the attached figures: 1. Inner conductor, 2. Outer conductor, 3. Signal input port, 4. Signal output port, 221. First gap, 222. Second gap. Detailed Implementation

[0020] This invention provides a coaxial dual stopband filter to solve the above-mentioned problems. In order to enable those skilled in the art to better understand the technical solution of this invention and to implement it, the technical solution of this invention will be clearly and thoroughly described below with reference to the accompanying drawings.

[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0022] Furthermore, it should be further explained that in the description of the embodiments of the present invention, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of the present invention, "multiple" means two or more.

[0023] The terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Thus, a feature defined as "first," "second," "third," or "fourth" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0024] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0025] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0026] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this invention are for illustrative purposes only and do not represent the only possible implementation.

[0027] Example 1 A coaxial dual stopband filter, such as Figure 1 and Figure 2 As shown, the structure includes an inner conductor 1, an outer conductor 2, an insulating dielectric, a signal input port 3, and a signal output port 4.

[0028] Specifically, the overall structure of the coaxial dual stopband filter is a coaxial cylinder, with an inner conductor 1, an insulating dielectric body, and an outer conductor 2 arranged coaxially from the inside to the outside.

[0029] In this embodiment, the insulating medium is air. Air has a relative permittivity of 1. Compared with other solid media, air has extremely low dielectric loss, good temperature stability, and high power capacity.

[0030] Signal input port 3 and signal output port 4 are located at both ends of the outer conductor 2 and are fixedly connected to the outer conductor 2, respectively, and are used to input signals and output signals.

[0031] Among them, the outer conductor 2 includes a metal cylinder, and both ends of the metal cylinder are fixedly connected to the signal input port 3 and the signal output port 4 respectively. Two defected ground structures symmetrically distributed with respect to the central plane of the outer conductor 2 are etched on the metal cylinder.

[0032] Among them, the materials of the inner conductor 1 and the outer conductor 2 are both selected as pure copper, corresponding to the purple copper with a copper content of ≥99.9% which has good electrical and thermal conductivity in actual production.

[0033] Specifically, as Figure 2 shown, the defected ground structure is a horizontally placed king-shaped structure. The defected ground structure includes a first slot 221 and three second slots 222. Among them, the three second slots 222 are parallel, and the length direction of the second slot 222 is parallel to the axial direction of the metal cylinder. The three second slots 222 are connected through the first slot 221, and the first slot 221 is located in the middle position of the second slot 222.

[0034] Specifically, the signal input port 3 is used to access signals, and the signal output port 4 is used to output signals. As one of the embodiments, according to the structure of the adapter, the structures of the signal input port 3 and the signal output port 4 can be the same or different.

[0035] Taking the signal input port 3 as an example for illustration, the signal input port 3 includes a first flange and a first adapter disposed in the middle of the first flange. The first flange can be preferably a rectangular or circular structure according to the different actual application scenarios. The first flange is fixedly connected to the metal cylinder. If the first flange is a rectangular structure, from the consideration of processability, it is recommended to make chamfered corners at the four corners of the rectangular structure to improve its safety.

[0036] In order to facilitate fixing its position, mounting holes can also be evenly distributed on the first flange. During use, connecting parts can be inserted into the mounting holes to connect the first flange with the fixing parts to fix the position of the coaxial dual-band stop filter.

[0037] Specifically, the signal output port 4 is used to output signals. The signal output port 4 includes a second flange and a second adapter disposed in the middle of the second flange. The second flange is fixedly connected to the other end of the metal cylinder, and the second adapter is connected to the other end of the inner conductor 1.

[0038] The first adapter and the second adapter can be preferably one of the coaxial SMA connectors, BNC connectors or TNC connectors according to the different connection objects.

[0039] In this embodiment, it is preferably a coaxial SMA connector, and the pin of the coaxial SMA connector is connected to the inner conductor 1.

[0040] In actual design, depending on the different objects to be plugged in, two male coaxial SMA connectors can be selected at the same time, or two female coaxial SMA connectors can be selected at the same time, or one male coaxial SMA connector and one female coaxial SMA connector can be selected and arranged on the first flange of signal input port 3 and the second flange of signal output port 4 respectively.

[0041] Figure 3 The diagram shows S-parameter curves corresponding to different lengths of the second gap 222 in the defective structure of this invention. Based on the electrical performance parameters, the optimal structural parameters that satisfy the electrical performance are determined to be: the length of the first gap 221 is 44 mm and the height is 2 mm; the length of the second gap 222 is 2 mm and the height is 44 mm; and the second gap 222 is centrally located on the metal cylinder. At this point, the center frequency of the first stopband is 0.89 GHz, which provides interference suppression greater than 17 dB; the center frequency of the second stopband is 1.63 GHz, which provides interference suppression greater than 25 dB.

[0042] Through electrical performance simulation, a method for adjusting the center frequency of the dual stopband filter provided by this invention was also obtained. One specific adjustment method is as follows: At the same time, the length of the second slit 222 is changed. As the length of the second slit 222 gradually increases, the center frequency of the first stopband and the center frequency of the second stopband will gradually decrease and move to lower frequencies.

[0043] The coaxial dual stopband filter provided by this invention has an insertion loss of less than 1.5dB outside the dual stopband frequency band of 0GHz-6GHz. It has low insertion loss and a wide passband range, which has little impact on the passage of electromagnetic waves in the normal frequency band and has a good filtering effect on interference signals in the stopband.

[0044] This invention utilizes a defective ground structure to increase distributed capacitance, alter the current distribution on the metal cylinder, introduce new resonant frequencies, increase the number of stopbands, and achieve dual-stopband filtering. This defective ground structure is novel and simple, effectively improving the current distribution in the metal structure and achieving high-performance dual-stopband filtering.

[0045] The coaxial dual-stopband filter provided by this invention has a dual-stopband frequency range applicable to the global 5G standard FR1 band, i.e., 0.45GHz-6.0GHz. It can be used to filter interference signals from important communication systems such as radar, microwave communication, and BeiDou satellites. Furthermore, the coaxial dual-stopband filter provided by this invention has a novel structure, featuring low passband insertion loss, excellent dual-stopband suppression performance, large power capacity, and ultra-wide suppression bandwidth. In actual manufacturing, the defective ground structure of the outer conductor layer is directly etched onto the metal layer, which not only reduces the overall size of the coaxial dual-stopband filter but also simplifies the structure and facilitates its fabrication, thus promoting integration and reducing the overall size of the coaxial dual-stopband filter.

[0046] The above-disclosed embodiments are merely preferred embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A coaxial dual-stopband filter, characterized in that, The device includes an inner conductor, an outer conductor, an insulating medium, a signal input port, and a signal output port. The inner conductor is coaxially fitted inside the outer conductor, and the insulating medium is located between the inner and outer conductors. The two ends of the inner conductor are respectively connected to the signal connection ends of the signal input port and the signal output port. The outer conductor includes a metal cylinder with its two ends fixedly connected to the signal input port and the signal output port, respectively. Two defect ground structures are provided on the metal cylinder, symmetrically distributed with respect to the central plane of the outer conductor. The defect ground structure includes a first gap and three parallel and spaced second gaps. The length direction of the second gaps is parallel to the axial direction of the metal cylinder, and the three second gaps are connected through the first gaps.

2. The coaxial dual stopband filter according to claim 1, characterized in that, The insulating medium used is polytetrafluoroethylene or air.

3. The coaxial dual stopband filter according to claim 1, characterized in that, Both the inner and outer conductors are made of pure copper.

4. The coaxial dual stopband filter according to claim 1, characterized in that, The length ratio of the first gap to the second gap is 22:1, and the height ratio of the first gap to the second gap is 1:

22.

5. The coaxial dual stopband filter according to claim 4, characterized in that, The first gap is located in the middle of the second gap.

6. The coaxial dual stopband filter according to claim 5, characterized in that, The second slit is centrally located on the metal cylinder.

7. The coaxial dual stopband filter according to claim 1, characterized in that, The signal input port includes a first flange and a first adapter disposed in the middle of the first flange. The first flange is fixedly connected to one end of the metal cylinder, and the first adapter is connected to one end of the inner conductor.

8. The coaxial dual stopband filter according to claim 7, characterized in that, The signal output port includes a second flange and a second adapter disposed in the middle of the second flange. The second flange is fixedly connected to the other end of the metal cylinder, and the second adapter is connected to the other end of the inner conductor.

9. The coaxial dual stopband filter according to claim 8, characterized in that, The first adapter and the second adapter are one of the following: coaxial SMA connector, BNC connector, or TNC connector.

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