High-power rectangular coaxial miniaturized microwave low-pass filter

Abstract

The invention discloses a high-power rectangular coaxial miniaturized microwave low-pass filter which comprises an outer conductor and an inner conductor, the inner conductor is arranged in the outer conductor and comprises three metal columns, and the three metal columns are divided into a first cylindrical inner conductor, a second cylindrical inner conductor and a third cylindrical inner conductor. The first cylindrical inner conductor, the second cylindrical inner conductor and the third cylindrical inner conductor are sequentially connected, a cover plate is arranged at the top of the outer conductor, the first cylindrical inner conductor and the third cylindrical inner conductor are in an open-circuit state at a certain distance from the upper-layer metal cover plate, and the other ends of the first cylindrical inner conductor and the third cylindrical inner conductor are fixed through a polyethylene support and connected with the outer conductor to form a low-impedance transmission line. By alternately arranging high and low impedance sections, a low-pass filtering characteristic is generated, the cut-off frequency can be flexibly adjusted by adjusting the lengths and radiuses of the first and third inner conductors, and the external size of the cavity is kept unchanged, so that the miniaturization design of the filter is realized; the filter is simple in structure and suitable for a high-performance microwave communication system.

Description

Technical Field

[0001] The invention relates to the technical field of microwave low-pass filters, in particular to a high-power rectangular coaxial miniaturized microwave low-pass filter. Background Art

[0002] Existing low-pass filters are widely used in microwave communication systems to suppress high-frequency signals and allow low-frequency signals to pass. However, traditional designs have many limitations. For example, although the planar microstrip filter has a simple structure, it has a low Q value and large insertion loss, which is not suitable for high-power applications. Although the traditional coaxial filter has a high Q value and low insertion loss, the inner conductor is designed to be connected end to end. Increasing the size of the inner conductor will increase the size of the entire circuit, resulting in the need to change the external dimensions when adjusting the frequency, which limits miniaturization and design flexibility. In addition, the traditional filter has insufficient high-order mode suppression capability in the stopband range, which affects the signal quality and system performance. Therefore, a high-power rectangular coaxial miniaturized microwave low-pass filter is proposed to solve the above problems. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the existing defects and provide a high-power rectangular coaxial miniaturized microwave low-pass filter. The inner conductor overcomes the defect of the traditional end-to-end connection. The newly designed inner conductor connection method ensures that the size of the outer conductor remains unchanged, that is, the size of the entire circuit remains unchanged. The cut-off frequency can be flexibly adjusted by adjusting the size of the inner conductor, which can effectively solve the problems in the background technology.

[0004] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a high-power rectangular coaxial miniaturized microwave low-pass filter, comprising an outer conductor and an inner conductor, the inner conductor is arranged inside the outer conductor, the inner conductor comprises three metal columns, the three metal columns are cylindrical inner conductor one, cylindrical inner conductor two and cylindrical inner conductor three, the cylindrical inner conductor one, cylindrical inner conductor two and cylindrical inner conductor three are connected in sequence, a cover plate is arranged at the bottom of the outer conductor, gaps are left between the upper ends of the cylindrical inner conductor one and the cylindrical inner conductor three and the cover plate respectively, two ends of the cylindrical inner conductor two are connected to the cylindrical inner conductor one and the cylindrical inner conductor three respectively, the lower ends of the cylindrical inner conductor one and the cylindrical inner conductor three are respectively arranged on polyethylene brackets, and the polyethylene brackets are arranged at the bottom of the outer conductor.

[0005] Furthermore, the cylindrical inner conductor 2 is suspended between the cylindrical inner conductor 1 and the cylindrical inner conductor 3.

[0006] Furthermore, the outer conductor is a metal rectangular cavity.

[0007] Furthermore, a coaxial feed line 1 and a coaxial feed line 2 are arranged on the outer side of the metal rectangular cavity.

[0008] Furthermore, the polyethylene support is composed of a polyethylene cylinder and a polyethylene disc, the lower end of the polyethylene cylinder is arranged on the polyethylene disc, the polyethylene disc is arranged at the bottom of the outer conductor, and the polyethylene support is arranged in a T-shaped structure.

[0009] Compared with the prior art, the present invention has the following beneficial effects: 1. A new type of inner conductor connection method is adopted to overcome the defects of the traditional end-to-end connection structure. While ensuring that the size of the conductor outside the cavity remains unchanged, by adjusting the length and radius of the inner conductor and the transmission line impedance ratio, this design achieves excellent performance of high Q value, high power and low insertion loss, while solving the limitations of traditional low-pass filters in flexibility and miniaturization, effectively suppressing high-order mode interference, ensuring the spectrum purity of signal transmission, and improving signal transmission quality.

[0010] 2. The circuit structure of the present invention is simple, and includes easy-to-process components such as a rectangular metal cavity, a cylindrical inner conductor, and a polyethylene support component. Compared with traditional complex designs, it greatly reduces production difficulty and manufacturing costs, while improving product stability and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 It is a simulation schematic diagram of the flexible and adjustable bandwidth of the present invention; Figure 3 It is a simulation schematic diagram of different inner conductor radius combinations of the present invention; Figure 4 It is a schematic diagram of the final simulation result of the present invention.

[0012] In the figure: 1 cylindrical inner conductor 1, 2 cylindrical inner conductor 2, 3 cylindrical inner conductor 3, 4 polyethylene cylinder 1, 5 polyethylene disk 1, 6 coaxial feed line 1, 7 polyethylene disk 2, 8 coaxial feed line 2, 9 metal rectangular cavity, 10 polyethylene cylinder 2, 11 cover plate. DETAILED DESCRIPTION

[0013] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0014] See also Figure 1-4The present invention provides a technical solution: a high-power rectangular coaxial miniaturized microwave low-pass filter, comprising an outer conductor and an inner conductor, wherein the inner conductor is arranged inside the outer conductor, the inner conductor comprises three metal columns, the three metal columns are respectively a cylindrical inner conductor 1, a cylindrical inner conductor 2 and a cylindrical inner conductor 3, the cylindrical inner conductor 1, the cylindrical inner conductor 2 and the cylindrical inner conductor 3 are connected in sequence, a cover plate 11 is arranged at the bottom of the outer conductor, and a gap is left between the upper ends of the cylindrical inner conductor 1 and the cylindrical inner conductor 3 and the cover plate 11, respectively, because the cylindrical inner conductor 1 and the cylindrical inner conductor 3 are respectively left between the cover plate 11 There is a certain gap so that the cylindrical inner conductor 1 and the cylindrical inner conductor 3 can be adjusted, that is, the cut-off frequency can be flexibly adjusted by adjusting the size of the inner conductor without causing changes in the cavity size, thereby ensuring the miniaturization design of the entire circuit. The entire circuit is integrated on the outer conductor, which effectively solves the problem of end-to-end connection in the traditional method. Increasing the size of the inner conductor will increase the size of the entire circuit. The two ends of the cylindrical inner conductor 2 are respectively connected to the cylindrical inner conductor 1 and the cylindrical inner conductor 3, and the lower ends of the cylindrical inner conductor 1 and the cylindrical inner conductor 3 are respectively arranged on polyethylene brackets, and the polyethylene brackets are arranged at the bottom of the outer conductor.

[0015] The cylindrical inner conductor 2 is suspended between the cylindrical inner conductor 1 and the cylindrical inner conductor 3. No grounding is formed between the outer conductor and the inner conductor. The outer conductor and the inner conductor form a high-low impedance line, thereby realizing a low-pass filter. At the 2.93 GHz stop band, the return loss reaches about 15 dB, which effectively suppresses high-order mode interference and improves the signal transmission quality.

[0016] The outer conductor is a metal rectangular cavity 9. Structurally, the rectangular structure of the outer conductor facilitates circuit integration.

[0017] The outer side of the metal rectangular cavity 9 is provided with a coaxial feed line 1 6 and a coaxial feed line 2 8. The coaxial feed line is used for input and output of signals. Its main function is to transmit external signals to the inside of the filter and output the signals after filtering.

[0018] The polyethylene bracket is composed of a polyethylene cylinder and a polyethylene disc. The lower end of the polyethylene cylinder is arranged on the polyethylene disc, and the polyethylene disc is arranged at the bottom of the outer conductor. The polyethylene bracket is arranged in a T-shaped structure. The polyethylene disc supports the lower end of the cylindrical inner conductor and also plays an isolation role. The polyethylene cylinder plays a role of limiting the specific cylindrical inner conductor. The interior of the outer conductor is provided with a polyethylene cylinder 14, a polyethylene cylinder 2 10, a polyethylene disc 15 and a polyethylene disc 27. The polyethylene cylinder 14 and the polyethylene disc 15 constitute a T-shaped polyethylene bracket. The lower end of the cylindrical inner conductor 3 is sleeved on the polyethylene disc 15. The polyethylene cylinder 2 10 and the polyethylene disc 27 constitute a T-shaped polyethylene bracket. The lower end of the cylindrical inner conductor 1 is sleeved on the polyethylene cylinder 2 10.

[0019] The cylindrical inner conductor 1 and the cylindrical inner conductor 3 can be adjusted on the T-shaped polyethylene bracket. The cylindrical inner conductor can be designed as a retractable structure, such as a threaded connection or a sliding guide joint structure. The length of the suspended end of the cylindrical inner conductor can be changed by rotating the thread or sliding the cylindrical inner conductor.

[0020] The cylindrical inner conductor can also be divided into multiple modules, which are assembled by plug-in or threaded connection. The total length of the inner conductor can be changed by adding or removing modules. In order to meet specific cut-off frequency requirements, cylindrical inner conductors of different lengths can be directly replaced to meet usage requirements. The above adjustable methods are all conventional structures, and the specific ones can be selected according to actual needs.

[0021] As attached Figure 2 As shown in the figure, the multiple curves correspond to different inner conductor lengths, indicating how to flexibly change the cutoff frequency by adjusting the inner conductor length under a fixed cavity size, as shown in the attached figure. Figure 3 As shown in the figure, the multiple curves correspond to different combinations of inner conductor radii, indicating how to flexibly change the cutoff frequency by adjusting the inner conductor radius without changing the size of the entire circuit. Figure 4 As shown, the red curve shows that below the cutoff frequency of 1.17GHz, the insertion loss is very small, with a minimum value of 0.0029dB, indicating that the low-frequency signal passes through almost without loss. In the stopband range, such as around 2.93GHz, the insertion loss increases rapidly to above -50dB, indicating that the high-frequency signal is effectively suppressed. The green curve shows that the filter has good input matching performance in the passband and stopband range, especially in the stopband, achieving high-order mode suppression effect.

[0022] The high-power rectangular coaxial miniaturized microwave low-pass filter of the present invention utilizes the electromagnetic coupling between the rectangular cavity of the outer conductor and the cylindrical inner conductor to form a high-low impedance transmission line to achieve low-pass filtering of the signal. The input signal is introduced through the coaxial feeder. The length and position of the inner conductor determine the cut-off frequency: a longer inner conductor increases the inductance and capacitance, thereby reducing the cut-off frequency, while a shorter inner conductor increases the cut-off frequency. Due to the suspended design of the upper ends of the cylindrical inner conductor 1 and the cylindrical inner conductor 3, the cut-off frequency can be flexibly adjusted by adjusting their lengths without changing the external dimensions of the cavity. At the same time, a low-pass filter with a minimum insertion loss of 0.0029 dB, a cut-off frequency of 1.17 GHz, and a return loss of about 15 dB at a 2.93 GHz stop band is achieved, meeting the high performance requirements of microwave communications.

[0023] The basic principles, main features and advantages of the present invention are shown and described above. Without departing from the spirit and scope of the present invention, the present invention may also be subject to various changes and improvements, which all fall within the scope of the present invention to be protected.

Claims

1. A high-power rectangular coaxial miniaturized microwave low-pass filter, comprising an outer conductor and an inner conductor, characterized in that: The inner conductor is arranged inside the outer conductor, and the inner conductor comprises three metal columns, which are respectively a cylindrical inner conductor one (1), a cylindrical inner conductor two (2) and a cylindrical inner conductor three (3). The cylindrical inner conductor one (1), the cylindrical inner conductor two (2) and the cylindrical inner conductor three (3) are connected in sequence. A cover plate (11) is arranged at the bottom of the outer conductor. Gaps are respectively left between the upper ends of the cylindrical inner conductor one (1) and the cylindrical inner conductor three (3) and the cover plate (11). The two ends of the cylindrical inner conductor two (2) are respectively connected to the cylindrical inner conductor one (1) and the cylindrical inner conductor three (3). The lower ends of the cylindrical inner conductor one (1) and the cylindrical inner conductor three (3) are respectively arranged on polyethylene brackets, and the polyethylene brackets are arranged at the bottom of the outer conductor.

2. A high-power rectangular coaxial miniaturized microwave low-pass filter according to claim 1, characterized in that: The cylindrical inner conductor 2 (2) is suspended between the cylindrical inner conductor 1 (1) and the cylindrical inner conductor 3 (3).

3. A high-power rectangular coaxial miniaturized microwave low-pass filter according to claim 1, characterized in that: The outer conductor is a metal rectangular cavity (9).

4. A high-power rectangular coaxial miniaturized microwave low-pass filter according to claim 1, characterized in that: A coaxial feed line 1 (6) and a coaxial feed line 2 (8) are arranged on the outer side surface of the metal rectangular cavity (9).

5. A high-power rectangular coaxial miniaturized microwave low-pass filter according to claim 1, characterized in that: The polyethylene support is composed of a polyethylene cylinder and a polyethylene disc. The lower end of the polyethylene cylinder is arranged on the polyethylene disc, the polyethylene disc is arranged at the bottom of the outer conductor, and the polyethylene support is arranged in a T-shaped structure.

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