A zero-adjustable band-pass filter

Abstract

The application relates to a zero-point adjustable band-pass filter, and belongs to the technical field of radio frequency microwave communication and radar, the structure of the filter comprising: a dielectric substrate, input and output transmission lines arranged at two ends of the dielectric substrate, the dielectric substrate being provided with a plurality of resonators and a cross-coupling line; the plurality of resonators are sequentially arranged on the dielectric substrate, and the plurality of resonators are arranged in an interdigital mode; the cross-coupling line is arranged on the side of the dielectric substrate, and the cross-coupling line is connected with the plurality of resonators; the application has the technical effect of improving the suppression ability of an out-of-band interference signal.

Description

Technical Field

[0001] This application relates to the technical fields of radio frequency microwave communication and radar, and in particular to a zero-point adjustable bandpass filter. Background Technology

[0002] With the development of wireless communication technology, military and civilian wireless communication systems are placing increasingly higher demands on microwave radio frequency communication systems. Microwave and millimeter-wave filters are among the most basic and critical components in microwave radio frequency communication systems, and they are widely used in civilian mobile communications and military radar, missile-borne, and spaceborne systems.

[0003] The continuous growth in demand for mobile communication in recent years has accelerated the development of microwave wireless communication systems. Today's high-quality wireless communication systems have increasingly higher requirements for the performance of microwave and millimeter-wave filters, such as lower insertion loss, better out-of-band rejection, and longer parasitic passband. Therefore, it is necessary to develop various new technologies to increase the utilization rate of spectrum resources.

[0004] Regarding the aforementioned technologies, the applicant believes that they suffer from insufficient out-of-band suppression performance. Utility Model Content

[0005] To address the aforementioned technical problems, this application provides a zero-adjustable bandpass filter.

[0006] This application provides a zero-point adjustable bandpass filter, which adopts the following technical solution: A zero-point adjustable bandpass filter includes a dielectric substrate, with an input transmission line and an output transmission line disposed at both ends of the dielectric substrate; the dielectric substrate is provided with a plurality of resonators and a cross-coupling line; the plurality of resonators are sequentially disposed on the dielectric substrate in an interdigital arrangement; the cross-coupling line is disposed on the side of the dielectric substrate and is connected to the plurality of resonators.

[0007] By adopting the above technical solution, the filter introduces a transmission zero in both the high and low stopbands of the passband by setting a cross-coupling line on the side of the dielectric substrate connected to the resonators arranged in an interdigital pattern. This achieves precise blocking of signals at specific frequencies, effectively solving the defect of insufficient out-of-band suppression in ordinary interdigital filters, and significantly improving the ability to suppress interference signals outside the passband. This meets the stringent requirements for signal isolation in scenarios with limited spectrum resources. The introduction of transmission zeros improves the stopband characteristics. While ensuring high selectivity of the filter, there is no need to optimize signal selection by increasing the filter order, thereby effectively reducing the filter order, lowering the insertion loss in the passband, and reducing the overall size of the filter. This meets the application requirements of modern microwave wireless systems for miniaturized and compact passive devices.

[0008] Preferably, the resonator includes a λ / 4 microstrip line resonant rod and a grounding hole, wherein the λ / 4 microstrip line resonant rod is disposed on the dielectric substrate; the grounding hole is formed on the dielectric substrate; and the λ / 4 microstrip line resonant rod is connected to the back side of the dielectric substrate through the grounding hole.

[0009] By adopting the above technical solution, the λ / 4 microstrip line resonant rod possesses inherent resonant frequency stability. Combined with the grounding connection between the grounding hole and the back of the dielectric substrate, it can effectively suppress parasitic radiation of the resonant rod, reduce energy loss, further reduce insertion loss in the filter passband, and improve signal transmission efficiency. The electrical length of the λ / 4 microstrip line resonant rod is only half that of the traditional half-wavelength resonant rod. Under the premise of achieving the same resonant frequency, the physical size of the resonant rod is significantly reduced. At the same time, the vertical connection of the grounding hole does not require additional lateral space on the surface of the dielectric substrate. Combined with the interdigital arrangement design, it further compresses the overall volume of the filter, meeting the needs of miniaturization and high-density integration in modern microwave systems.

[0010] Preferably, the input transmission line is the signal input terminal of the filter, and the output terminal of the output transmission line is the signal output terminal of the filter.

[0011] By adopting the above technical solution, the input transmission line and the output transmission line respectively undertake the functions of signal input and output, which can ensure that the signal transmission path at both ends of the filter is symmetrical, reduce signal reflection and phase distortion caused by path asymmetry, and improve the consistency and stability of signal transmission within the passband.

[0012] Preferably, the λ / 4 microstrip line resonant rod is a quarter-wavelength microstrip line resonant rod; the length of the λ / 4 microstrip line resonant rod of each resonator and the width of the λ / 4 microstrip line resonant rod of each resonator are different.

[0013] By adopting the above technical solution, the λ / 4 microstrip line resonator rods of each resonator are designed with unequal lengths and widths. Utilizing the strong correlation between microstrip line size and resonant frequency, the resonant frequency of each resonator can be independently adjusted, enabling the filter to accurately match the target passband frequency range. At the same time, it provides support for frequency fine-tuning of the transmission zeros at the high and low ends of the passband and stopband, improving the filter's adaptability to the frequency requirements of different application scenarios. The unequal length and width of the λ / 4 microstrip line resonator rods can flexibly adjust the electromagnetic coupling strength and coupling phase between resonators. Combined with the effect of the side cross coupling lines, it can further enhance the blocking effect of the transmission zeros on interference signals, optimize the steepness of the filter's transition band, significantly improve filter selectivity, and better meet the needs of accurate screening of adjacent channel signals in scenarios with congested spectrum resources.

[0014] Preferably, the number of resonators is 2N+1, where N is an integer greater than or equal to zero.

[0015] By adopting the above technical solution, the odd-numbered configuration of 2N+1 resonators can make the connection points of the side cross-coupling lines and resonators more evenly distributed, enhance the stability of the transmission zeros introduced by the cross-coupling, avoid the coupling phase cancellation problem caused by the even number of resonators, ensure that the transmission zero frequencies of the high and low end stopbands are accurately controllable, and further improve the reliability of out-of-band suppression.

[0016] Preferably, one end of the cross-coupling line is connected to the end of the Nth λ / 4 microstrip line resonant rod furthest from the grounding hole, and the other end of the cross-coupling line is connected to the end of the N+2th λ / 4 microstrip line resonant rod furthest from the grounding hole.

[0017] By adopting the above technical solution, this cross-coupling connection method can form a specific electromagnetic coupling path between resonators. By adjusting the coupling phase and strength, transmission zeros can be accurately generated in the high and low stopbands of the passband, and the zero frequency can be flexibly adjusted with the coupling line parameters. This effectively solves the problem of insufficient out-of-band suppression of ordinary interdigital filters and significantly improves the blocking effect on interference signals in adjacent frequency bands. The cross-coupling line is connected to the end of the resonant rod away from the grounding hole. This position is the current antinode region of the resonant rod, which can maximize the coupling efficiency. At the same time, this connection method will not destroy the inherent resonant characteristics of the resonator, nor will it interfere with the transmission path of the input and output signals. This ensures low insertion loss and good phase linearity in the passband of the filter, and achieves synergistic optimization of stopband suppression and passband performance.

[0018] Preferably, the input transmission line and the output transmission line are symmetrically distributed along the geometric center line of the dielectric substrate; the plurality of resonators and the cross-coupled lines are symmetrically distributed along the geometric center line of the dielectric substrate.

[0019] By adopting the above technical solution, the fully symmetrical layout of the structure ensures that the signal transmission path at the input and output ends of the filter is completely consistent. The symmetrical distribution of the resonator and the cross-coupled line also keeps the electromagnetic coupling characteristics on both sides of the passband balanced, effectively avoiding problems such as passband frequency response distortion and inconsistent transition band steepness caused by structural asymmetry. This ensures that the center frequency of the filter passband is stable, and the transmission zero-point suppression effect of the high and low end stopbands is symmetrical, thereby improving the accuracy of signal selection.

[0020] In summary, this application includes at least one of the following beneficial technical effects: 1. The λ / 4 microstrip line resonant rod possesses inherent resonant frequency stability. Combined with the grounding connection between the grounding hole and the back of the dielectric substrate, it can effectively suppress parasitic radiation of the resonant rod, reduce energy loss, further reduce insertion loss in the filter passband, and improve signal transmission efficiency. The electrical length of the λ / 4 microstrip line resonant rod is only half that of the traditional half-wavelength resonant rod. Under the premise of achieving the same resonant frequency, the physical size of the resonant rod is significantly reduced. At the same time, the vertical connection of the grounding hole does not require additional lateral space on the surface of the dielectric substrate. Combined with the interdigital arrangement design, it further compresses the overall volume of the filter, meeting the needs of miniaturization and high-density integration in modern microwave systems.

[0021] 2. This cross-coupling connection method can form a specific electromagnetic coupling path between resonators. By adjusting the coupling phase and strength, transmission zeros can be accurately generated at the high and low end of the passband and stopband. The zero frequency can be flexibly adjusted according to the coupling line parameters, effectively solving the problem of insufficient out-of-band suppression of ordinary interdigital filters and significantly improving the blocking effect on interference signals in adjacent frequency bands. The cross-coupling line is connected to the end of the resonant rod away from the grounding hole. This position is the current antinode region of the resonant rod, which can maximize the coupling efficiency. At the same time, this connection method will not destroy the inherent resonant characteristics of the resonator, nor will it interfere with the transmission path of the input and output signals, ensuring low insertion loss and good phase linearity in the passband of the filter, and achieving synergistic optimization of stopband suppression and passband performance. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure in the embodiment.

[0023] Explanation of reference numerals in the attached figures: 1. Dielectric substrate; 11. Input transmission line; 12. Output transmission line; 2. Resonator; 21. λ / 4 microstrip line resonator rod; 22. Grounding hole; 3. Cross-coupled line. Detailed Implementation

[0024] The following is in conjunction with the appendix Figure 1 This application will be described in further detail.

[0025] This application discloses a zero-point adjustable bandpass filter. (Refer to...) Figure 1 The filter includes a dielectric substrate 1, which is made of conductive material to form metal lines and vias. Input transmission lines 11 and output transmission lines 12 are provided at both ends of the dielectric substrate 1. The input transmission lines 11 and output transmission lines 12 are symmetrically distributed along the geometric center line of the dielectric substrate 1. The input transmission lines 11 are the signal input terminals of the filter, and the output terminals of the output transmission lines 12 are the signal output terminals of the filter.

[0026] The dielectric substrate 1 is provided with multiple resonators 2 and cross-coupled lines 3; the multiple resonators 2 are sequentially arranged on the dielectric substrate 1, and each resonator 2 includes a λ / 4 microstrip line resonant rod 21 and a grounding hole 22. The λ / 4 microstrip line resonant rod 21 is arranged on the dielectric substrate 1; the grounding hole 22 is formed on the dielectric substrate 1; the λ / 4 microstrip line resonant rod 21 is connected to the back side of the dielectric substrate 1 through the grounding hole 22; the multiple resonators 2 are arranged in an interdigital pattern, that is, one end of the grounding hole 22 of all resonators 2 is on a different side; the number of resonators 2 is 2N+1, where N is an integer greater than or equal to zero.

[0027] A cross-coupling line 3 is disposed on the side of the dielectric substrate 1 and is connected to multiple resonators 2. The multiple resonators 2 and the cross-coupling line 3 are symmetrically distributed along the geometric center line of the dielectric substrate 1. One end of the cross-coupling line 3 is connected to the end of the Nth λ / 4 microstrip line resonator 21 that is away from the grounding hole 22, and the other end of the cross-coupling line 3 is connected to the end of the N+2th λ / 4 microstrip line resonator 21 that is away from the grounding hole 22. The low-end zero point of the filter can be adjusted by changing the length, thickness and distance of the cross-coupling line 3 to the λ / 4 microstrip line resonator 21.

[0028] The working principle of the zero-point adjustable bandpass filter in this application is as follows: an external radio frequency signal is fed into the dielectric substrate 1 through the input transmission line 11. The input transmission line 11 is electromagnetically coupled to the first λ / 4 microstrip line resonator 21, transferring the signal energy to the resonator 2. Since the resonator 2 is a λ / 4 microstrip line structure, and one end is connected to the back of the dielectric substrate 1 through a grounding hole 22, when the frequency of the input signal approaches the λ / 4... When the microstrip line reaches its inherent resonant frequency, resonator 2 is excited and generates a strong resonant response; conversely, signals deviating from the resonant frequency are difficult to excite resonator 2, and energy cannot be effectively transferred. Multiple resonators 2 are arranged in an interdigital configuration, and the grounding holes 22 of all resonators 2 are distributed on different sides. This arrangement increases the electromagnetic coupling area and coupling strength between adjacent resonators 2. The first excited resonator 2 transfers energy to the next resonator 2 through electromagnetic coupling, and so on, with energy being coupled and transmitted step by step between 2N+1 resonators 2. Since the filter as a whole is symmetrically distributed along the geometric centerline of the dielectric substrate 1, and the input transmission line 11 and the output transmission line 12 are symmetrically arranged, the symmetry of the signal during transmission is ensured, reducing port reflection and signal distortion. The cross-coupling line 3 located on the side of the dielectric substrate 1 connects one end to the end of the Nth λ / 4 microstrip line resonator rod 21 that is away from the grounding hole 22, and the other end to the N+2th resonator rod. The end furthest from the grounding hole 22 forms a cross-coupling path. The electromagnetic coupling generated between the cross-coupling line 3 and the resonator 2 introduces a transmission zero. The position of this zero can be precisely adjusted by adjusting the length, thickness, and distance to the λ / 4 microstrip line resonator rod 21 of the cross-coupling line 3. When the electromagnetic coupling phase of the cross-coupling line 3 is opposite to the direct coupling phase between the resonators 2, a transmission zero will be formed at the low end of the filter passband. This zero can suppress interference signals at the low end of the passband, improve the out-of-band rejection capability of the filter, and optimize the transition characteristics between the passband and the stopband. The signal transmitted through the multi-stage resonators 2 retains only the frequency band consistent with the inherent resonant frequency of the resonator 2. These signals are coupled to the output transmission line 12 through the last resonator 2 and finally output from the output end. Signals outside the passband either cannot excite the resonator 2 or are suppressed by the transmission zero introduced by the cross-coupling and cannot pass through the filter, thus realizing the function of bandpass filtering.

[0029] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A zero-tunable bandpass filter, characterized in that: The device includes a dielectric substrate (1), with an input transmission line (11) and an output transmission line (12) at both ends; the dielectric substrate (1) is provided with a plurality of resonators (2) and a cross-coupling line (3); the plurality of resonators (2) are sequentially disposed on the dielectric substrate (1) and are arranged in an interdigital pattern; the cross-coupling line (3) is disposed on the side of the dielectric substrate (1) and is connected to the plurality of resonators (2).

2. The zero-point adjustable bandpass filter according to claim 1, characterized in that: The resonator (2) includes a λ / 4 microstrip line resonant rod (21) and a grounding hole (22). The λ / 4 microstrip line resonant rod (21) is disposed on the dielectric substrate (1). The grounding hole (22) is formed on the dielectric substrate (1). The λ / 4 microstrip line resonant rod (21) is connected to the back side of the dielectric substrate (1) through the grounding hole (22).

3. A zero-adjustable bandpass filter according to claim 1, characterized in that: The input transmission line (11) is the signal input terminal of the filter, and the output transmission line (12) is the signal output terminal of the filter.

4. A zero-adjustable bandpass filter according to claim 2, characterized in that: The λ / 4 microstrip line resonant rod (21) is a resonant rod with a quarter-wavelength microstrip line structure; the length of the λ / 4 microstrip line resonant rod (21) of each resonator (2) and the width of the λ / 4 microstrip line resonant rod (21) of each resonator (2) are different.

5. A zero-adjustable bandpass filter according to claim 2, characterized in that: The number of resonators (2) is 2N+1, where N is an integer greater than or equal to zero.

6. A zero-adjustable bandpass filter according to claim 5, characterized in that: One end of the cross coupling line (3) is connected to the end of the Nth λ / 4 microstrip line resonator (21) that is away from the grounding hole (22), and the other end of the cross coupling line (3) is connected to the end of the N+2th λ / 4 microstrip line resonator (21) that is away from the grounding hole (22).

7. A zero-adjustable bandpass filter according to claim 1, characterized in that: The input transmission line (11) and the output transmission line (12) are symmetrically distributed along the geometric center line of the dielectric substrate (1); the plurality of resonators (2) and the cross-coupled line (3) are symmetrically distributed along the geometric center line of the dielectric substrate (1).

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