A cavity electrically tunable preselection filter

Abstract

This invention discloses a cavity electrically tunable preselection filter, relating to the field of wireless communication equipment. It includes a mounting cavity and a PCB board. The PCB board is fixed to the mounting cavity via connectors and houses an integrated circuit and a coil assembly. The mounting cavity contains four resonant cavities and two circuit-shielded resonant cavities. The four resonant cavities are arranged side-by-side along the length of the mounting cavity. The two circuit-shielded resonant cavities are arranged side-by-side along the width of the mounting cavity and located in the middle of the four resonant cavities, serving to shield the integrated circuit and provide resonance for the resonant cavities on either side. The coil assembly includes four coils for specific frequency bands. The four coils are electrically connected to the PCB board and located within the four resonant cavities. It features a compact structure, excellent filtering performance, and adaptability to complex electromagnetic environments.

Description

Technical Field

[0001] This utility model relates to the field of wireless communication equipment, and more specifically, to a cavity electrically tunable preselection filter. Background Technology

[0002] The performance of front-end filters is crucial to the performance of wireless telecommunications equipment. Although the development of digital technology has enabled digital filters to replace analog filters in the baseband and even intermediate frequency sections, the radio frequency (RF) filters remain irreplaceable, as they determine the overall sensitivity and anti-interference capability of the device.

[0003] Traditional filters use fixed bandwidth and fixed frequency. The filter bandwidth cannot be adjusted according to the actual received signal, resulting in problems such as large size, complex control, and poor performance. Utility Model Content

[0004] The purpose of this invention is to provide a cavity electrically tunable preselective filter, which has a compact structure, excellent filtering performance, and can adapt to complex electromagnetic environments.

[0005] The embodiments of this utility model are implemented as follows:

[0006] This application provides a cavity electrically tunable preselection filter, including:

[0007] The mounting cavity and PCB board are installed. The PCB board is fixed to the mounting cavity by a connector. The PCB board is provided with integrated circuits and coil assemblies.

[0008] The mounting cavity is provided with four resonant cavities and two circuit-shielded resonant cavities. The four resonant cavities are arranged side by side along the length of the mounting cavity. The two circuit-shielded resonant cavities are arranged side by side along the width of the mounting cavity and are located in the middle of the four resonant cavities. They are used to shield the integrated circuit and to provide resonance for the resonant cavities on both sides.

[0009] The coil assembly includes four coils for specific frequency bands; the four coils are electrically connected to the PCB board and located in the four resonant cavities.

[0010] Furthermore, based on the aforementioned scheme, the four resonant cavities and the two circuit-shielded common resonant cavities are all separated by an integrally formed partition plate, and a positioning post is integrally inserted at the end and middle of the partition plate; a positioning hole is opened at the top of the positioning post;

[0011] The PCB board has multiple connection holes, each of which corresponds to a positioning hole and is connected via the connector.

[0012] Furthermore, based on the aforementioned scheme, bosses are provided at the four corners of the mounting cavity, and the bosses are provided with fixing holes for fixing the filter as a whole.

[0013] Furthermore, based on the aforementioned scheme, the mounting cavity is made of copper-aluminum alloy.

[0014] Furthermore, based on the aforementioned scheme, the inner wall and outer wall of the mounting cavity are smooth surfaces after polishing, with the inner wall polishing accuracy being Ra≤0.025μm and the outer wall polishing accuracy being Ra≤0.05μm.

[0015] Furthermore, based on the aforementioned scheme, both the inner and outer walls of the mounting cavity are provided with a gold plating layer, the thickness of which is ≥0.5μm.

[0016] Furthermore, based on the aforementioned scheme, the coil is a 0.35×16 enameled wire.

[0017] Furthermore, based on the aforementioned solution, the gap between the PCB board and the mounting cavity is ≤0.1mm.

[0018] Furthermore, based on the aforementioned solution, the connector is a PM1.2×4 screw.

[0019] Compared with the prior art, the embodiments of this utility model have at least the following advantages or beneficial effects:

[0020] This application achieves wide-band signal coverage and meets dynamic tuning requirements by setting four resonant cavities arranged in parallel along the length direction and cooperating with coils of specific frequency bands. Two circuit-shielded resonant cavities are located in the middle of the resonant cavities. On the one hand, they can effectively shield the electromagnetic interference generated by the integrated circuits on the PCB board and avoid interfering with the standing wave resonance of the resonant cavities. On the other hand, they form resonant coupling on both sides of the resonant cavities, enhancing resonance consistency and stability and improving filtering accuracy. The fixed structure of the PCB board and the mounting cavity improves the overall integration level and reduces the size of the device. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the overall structure of the cavity electrically adjustable preselection filter according to an embodiment of the present invention;

[0023] Figure 2This is a top view of the cavity electrically adjustable preselection filter according to an embodiment of the present invention;

[0024] Figure 3 This is a top view of the PCB board of an embodiment of this utility model.

[0025] Icons: 1-Mounting cavity, 11-Resonant cavity, 12-Circuit shielded resonant cavity, 13-Blocking plate, 14-Positioning post, 15-Positioning hole, 16-Boss, 17-Fixing hole, 2-PCB board, 21-Integrated circuit, 22-Coil, 23-Connection hole. Detailed Implementation

[0026] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0027] Please refer to Figures 1-3 The diagram shown is a schematic representation of the overall structure of a cavity electrically tunable preselector filter.

[0028] This embodiment provides a cavity electrically tunable preselection filter, including:

[0029] The mounting cavity 1 and PCB board 2 are installed. The PCB board 2 is fixed to the mounting cavity 1 by a connector. The PCB board 2 is provided with integrated circuit 21 and coil 22 assembly.

[0030] The mounting cavity 1 is provided with four resonant cavities 11 and two circuit-shielded common resonant cavities 12. The four resonant cavities 11 are arranged side by side along the length of the mounting cavity 1; the two circuit-shielded common resonant cavities 12 are arranged side by side along the width of the mounting cavity 1 and are located in the middle of the four resonant cavities 11. They are used to shield the integrated circuit 21 and to play a resonant role on the resonant cavities 11 on both sides.

[0031] The coil 22 assembly includes four coils 22 for specific frequency bands; the four coils 22 are electrically connected to the PCB board 2 and are located in four resonant cavities 11.

[0032] The following will further describe an electrically tunable preselection filter of cavity according to this exemplary embodiment.

[0033] In some embodiments, the mounting cavity 1 is made of copper-aluminum alloy and is integrally formed by CNC machining of four resonant cavities 11 arranged side by side along the length direction and two circuit-shielded common resonant cavities 12 located in the middle and arranged side by side along the width direction. A PCB board 2 is fixed to the mounting cavity 1 by connectors, and an integrated circuit 21 and a coil 22 assembly are disposed on the PCB board 2. The two circuit-shielded common resonant cavities 12 are hollow rectangular structures, namely the left circuit-shielded common resonant cavity 12 and the right circuit-shielded common resonant cavity 12, used to shield the integrated circuit 21 and to provide resonance for the resonant cavities 11 on both sides. The coil 22 assembly includes four coils 22 of specific frequency bands, which are electrically connected to the PCB board 2 and located within the four resonant cavities 11.

[0034] By setting up four resonant cavities 11 arranged side by side along the length, and cooperating with coils 22 of a specific frequency band, signal coverage in a wide frequency range of 1.6-678MHz can be achieved, meeting the requirements of dynamic tuning. Two circuit-shielded common resonant cavities 12 are located in the middle of the resonant cavities 11. On the one hand, they effectively shield the electromagnetic interference generated by the integrated circuit 21 on the PCB board, avoiding interference with the standing wave resonance of the resonant cavity 11. On the other hand, they form common resonant coupling on both sides of the resonant cavities 11, enhancing resonance consistency and stability, and improving filtering accuracy (e.g., out-of-band rejection ≥60dB). The fixed structure of the PCB board and the mounting cavity 1 improves the overall integration level and reduces the size of the device.

[0035] The filter employs a cascaded arrangement of multiple independent resonant cavities 11, each resonating for signals within a specific frequency range. By precisely designing the size, shape, and coupling structure of the resonant cavities 11, the entire filter can cover a wide frequency band of 1.6-678MHz. Simultaneously, the cascaded structure helps improve the filter's frequency selectivity and stability, providing the basic architecture for rapid tuning. For example, when the input signal frequency changes, the individual resonant cavities 11 can respond quickly and work collaboratively to filter and process different frequency components.

[0036] In a preferred embodiment, the four resonant cavities 11 and the two circuit-shielded common resonant cavities 12 are separated by an integrally formed partition 13. Positioning posts 14 are integrally inserted at the ends and middle of the partition 13; positioning holes 15 are formed at the top of the positioning posts 14; the PCB board 2 has multiple connecting holes 23, each corresponding to a positioning hole 15, and connected via connectors. The integrally formed partition 13 ensures the structural rigidity and positional accuracy of the resonant cavities 11 and the circuit-shielded common resonant cavities 12, avoiding resonant frequency shifts due to assembly errors. The cooperation between the positioning posts 14 and the connecting holes 23 achieves precise positioning of the PCB board and the mounting cavity 1, ensuring the relative position stability of the coil 22 and the resonant cavity 11, further improving the consistency of filtering performance. During installation, coarse positioning is achieved through the positioning holes 15 of the positioning posts 14 and the through holes on the PCB board 2, and then the connectors are inserted for precise calibration.

[0037] In a preferred embodiment, the mounting cavity 1 is provided with bosses 16 at each of its four corners, and each boss 16 has fixing holes 17 for fixing the filter assembly. The fixing holes 17 of the four corner bosses 16 facilitate fixing the filter assembly to external equipment (such as transceivers or radios), reducing the impact of vibration or displacement during use on the filtering performance and enhancing the stability of equipment operation.

[0038] As a preferred embodiment, the mounting cavity 1 is made of copper-aluminum alloy. Copper-aluminum alloy has excellent electrical and thermal conductivity, which can reduce the transmission loss of electromagnetic waves in the cavity, improve the Q value of the resonant cavity 11, and provide a basis for low insertion loss (≤1.2dB).

[0039] As a preferred implementation method, to ensure good resonance performance of the cavity, its interior must be polished until burrs are removed. The polishing precision of the inner wall is Ra≤0.025μm, and the polishing precision of the outer wall is Ra≤0.05μm. Specifically, the inner wall of the mounting cavity 1 is polished to ensure a precision of Ra≤0.025μm; the outer wall is polished to Ra≤0.05μm. This high-precision polishing reduces electromagnetic wave reflection and scattering losses on the inner wall of the cavity, reduces signal attenuation, and provides a good surface foundation for subsequent gold plating processes.

[0040] As a preferred implementation, to enhance the smoothness of the cavity interior, a gold plating process is used inside the housing. Since the cavity filter is made of copper alloy, which is prone to ion displacement reactions within the integrated circuit 21 structure, an external gold plating process is employed to solidify the surface, with a gold plating layer thickness ≥0.5μm. Specifically, after polishing, 24K gold is electroplated on both the inner and outer walls, with the gold plating layer thickness controlled at ≥0.5μm. This ≥0.5μm gold plating layer further enhances the conductivity and smoothness of the cavity surface, reduces oxidation and ion displacement reactions, extends equipment lifespan, and simultaneously improves electromagnetic shielding effectiveness and resonance stability.

[0041] The filter cavity is made of copper-aluminum alloy, which has excellent conductivity and low RF loss. Simultaneously, the inner and outer surfaces of the cavity undergo high-precision polishing, with the inner wall polishing precision reaching Ra≤0.025μm and the back surface polishing precision reaching Ra≤0.05μm. This significantly reduces electromagnetic wave reflection and scattering losses on the cavity's inner walls. Subsequently, both inner and outer surfaces are plated with 24K gold, with a plating thickness ≥0.5μm. The gold plating not only further enhances surface smoothness but also effectively prevents ion replacement reactions, solidifying the surface state and further reducing signal transmission losses. This ensures the filter has a high Q value and effectively reduces insertion loss.

[0042] As a preferred implementation, the coil 22 is made of 0.35mm×16μm enameled wire. The 0.35×16 enameled wire coil 22 can accurately match the resonance requirements of a specific frequency band. By adjusting the inductance characteristics of the coil 22, rapid tuning (microsecond level) can be achieved, ensuring efficient coupling of signals in different frequency bands.

[0043] As a preferred embodiment, the gap between the PCB board 2 and the mounting cavity 1 is ≤0.1mm, which reduces electromagnetic leakage between the two, enhances the energy coupling efficiency between the coil 22 and the resonant cavity 11, and reduces insertion loss.

[0044] As a preferred implementation, the aforementioned connector is a PM1.2×4 screw. The PM1.2×4 screw can achieve a tight fixation between the PCB board and the mounting cavity 1, avoiding positional displacement caused by loosening. At the same time, the small size design is suitable for a compact structure and does not affect the internal electromagnetic environment.

[0045] The pretreatment of the enameled wire and coil 22 is as follows:

[0046] 1. Wire fixing: Lay the 0.35×16 enameled wire flat on the anti-static table and use a non-metallic weight (such as a nylon weight block) to press the wire end firmly to prevent the wire from slipping or the enamel from being scratched; cut the enameled wire to the reserved length (it is recommended to extend it 20mm beyond the soldering point).

[0047] 2. Positioning and Enamel Treatment of Coil 22 (Taking 350-400M coil 22 as an example)

[0048] Hold coil 22 in your left hand, keeping the second coil facing the operator; use a diamond file in your right hand to lightly file along the axis of the second coil of coil 22 at a 45° angle, removing the paint with a width ≤0.8mm to expose the metallic luster (avoid scratching the substrate).

[0049] The enameled wire is soldered as follows:

[0050] 1. Hold the soldering iron in your right hand and gently touch the target position of the enameled wire to burn through the enamel coating through heat conduction (contact time ≤ 5 seconds). Then use your left hand to feed the solder wire to complete the pre-tinning.

[0051] 2. Attach the pre-tinned enameled wire end to the file-open part of the second coil of coil 22; apply pressure to the solder joint with the soldering iron tip at a 90° angle, and control the solder melting time within 5 seconds to form a straight solder joint (the solder should cover ≥90% of the metal contact surface).

[0052] 3. The remaining 3 coils 22 are processed in the same way. The soldering iron tip must be cleaned after each coil 22 is completed (to prevent oxide residue). The soldering interval is ≥5 seconds to avoid the soldering iron from overheating and deforming the coil 22 frame.

[0053] The specific frequency band coil 22 installed in each resonant cavity 11 is one of the key components for frequency tuning. The coil 22 is made of 0.35×16 enameled wire and undergoes special enamel treatment and soldering processes for different frequency bands. Taking the 350-400MHz coil 22 as an example, the enamel is filed open at a 45° angle along the second coil axis and then soldered. This design allows the coil 22 to precisely adjust its inductance characteristics at different frequency bands. When the applied voltage or magnetic field changes, the equivalent inductance of the coil 22 changes accordingly, thereby changing the resonant frequency of the resonant cavity 11, achieving rapid response and tuning to different frequency signals.

[0054] The overall assembly process of the filter is as follows: Insert four coils 22 vertically through the mounting holes on PCB board 2, ensuring the bottom of each coil 22 is flush with the surface of PCB board 2. After flipping the PCB, insert it into the mounting cavity 1 base. Coarse calibration is achieved using the positioning pins 14 of mounting cavity 1. Use a soldering iron to perform single-point symmetrical soldering on the coil 22 pins, prioritizing the fixing of diagonal pins to prevent misalignment. Insert PCB board 2 (IC side up) and perform fine calibration using screws. Tighten the 12 PM1.2×4 screws twice in diagonal order (first pre-tightening to 50% torque, then full torque tightening). The final result should be a gap between the board and the cavity ≤0.1mm, with no stripped screw heads. After assembly, manually shake the cavity to confirm there are no abnormal noises or looseness. Use a feeler gauge to check the uniformity of the gap between the PCB and the cavity. Perform electrical testing, measuring the insulation resistance between coils 22 with a multimeter (>10MΩ@500V). After powering on, measure the reference voltage of PCB board 2 (error <±2%).

[0055] After assembly, the filter can achieve fast tuning in the range of 1.6-678MHz by adjusting the equivalent inductance / capacitance of coil 22 (such as by applying voltage or magnetic field), and has excellent performance such as low insertion loss and high out-of-band rejection.

[0056] The beneficial effects of the embodiments of this application are as follows:

[0057] Excellent performance: It achieves fast tuning (microsecond level) in the frequency range of 1.6-678MHz, insertion loss ≤1.2dB, receive noise ≤1.5dB, 1dB bandwidth ≤1%, and out-of-band rejection ≥60dB at 15% of the intermediate frequency, which improves the anti-interference capability and receiving sensitivity of the device.

[0058] Structural optimization: The multi-cavity cascaded synchronous tuning design avoids passband distortion, and the left and right circuit shielded common resonant cavities 12 enhance anti-interference capabilities. The copper-aluminum alloy cavity with gold plating process ensures high Q value and low loss.

[0059] Miniaturization and integration: Utilizing precision CNC machining and a compact layout, it is small in size and light in weight, solving the problem of the large size of traditional filters.

[0060] Domestic substitution: Breaking the foreign technology monopoly, it is suitable for shortwave and ultra-shortwave transceivers, radios and other equipment, and can achieve stable reception of weak signals in complex electromagnetic environments.

[0061] Furthermore, unless otherwise explicitly specified or limited, the terms "installation" and "connection" in this application embodiment should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. The terms "upper," "lower," "left," "right," "inner," "outer," and "side," etc., are merely for reference to the direction in the accompanying drawings or the usual placement of the product during use. They are only for clearly describing this application and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. They should not be construed as limitations on this application. The terms "first," "second," etc., are only used for distinguishing descriptions and should not be construed as indicating or implying relative importance; "multiple" refers to at least two. In this application embodiment, the limitations on relative positional relationships such as parallel, perpendicular, and aligned are all relative to the current technological level and are not absolutely strict limitations. Slight deviations are allowed; approximations of parallel, perpendicular, and aligned are all acceptable. For example, "A and B are parallel" means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 degrees and 10 degrees.

[0062] The above are only some embodiments and implementation methods of this application. The protection scope of this application is not limited thereto. In the absence of conflict, the embodiments and features in the embodiments of this application can be combined with each other. Any combination of features in different embodiments is also within the protection scope of this application. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the protection scope of this application.

Claims

1. A cavity electrically adjustable preselection filter, characterized in that, include: The mounting cavity and PCB board are installed. The PCB board is fixed to the mounting cavity by a connector. The PCB board is provided with integrated circuits and coil assemblies. The mounting cavity is provided with four resonant cavities and two circuit-shielded resonant cavities. The four resonant cavities are arranged side by side along the length of the mounting cavity. The two circuit-shielded resonant cavities are arranged side by side along the width of the mounting cavity and are located in the middle of the four resonant cavities. They are used to shield the integrated circuit and to provide resonance for the resonant cavities on both sides. The coil assembly includes four coils for specific frequency bands; the four coils are electrically connected to the PCB board and located in the four resonant cavities.

2. The cavity electrically adjustable preselection filter according to claim 1, characterized in that, The four resonant cavities and the two circuit-shielded common resonant cavities are all separated by an integrally formed partition plate, and a positioning post is integrally inserted at the end and middle of the partition plate; a positioning hole is opened at the top of the positioning post; The PCB board has multiple connection holes, each of which corresponds to a positioning hole and is connected via the connector.

3. The cavity electrically adjustable preselection filter according to claim 2, characterized in that, The mounting cavity is provided with bosses at the four corners, and each boss has a fixing hole for fixing the filter as a whole.

4. The cavity electrically adjustable preselection filter according to claim 3, characterized in that, The mounting cavity is made of copper-aluminum alloy.

5. The cavity electrically adjustable preselection filter according to claim 4, characterized in that, The inner and outer walls of the mounting cavity are smooth surfaces after polishing, with the inner wall polishing accuracy being Ra≤0.025μm and the outer wall polishing accuracy being Ra≤0.05μm.

6. The cavity electrically adjustable preselection filter according to claim 5, characterized in that, Both the inner and outer walls of the mounting cavity are provided with a gold plating layer, and the thickness of the gold plating layer is ≥0.5μm.

7. The cavity electrically adjustable preselection filter according to claim 1, characterized in that, The coil is made of 0.35×16 enameled wire.

8. The cavity electrically adjustable preselection filter according to claim 1, characterized in that, The gap between the PCB board and the mounting cavity is ≤0.1mm.

9. The cavity electrically adjustable preselection filter according to claim 2, characterized in that, The connector is a PM1.2×4 screw.

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