High-frequency crystal filter structure

Abstract

The utility model discloses a high-frequency crystal filter structure, and particularly relates to the technical field of design and manufacture of crystal filters for communication navigation, which comprises a box body, a bottom plate base is arranged on the lower surface inside the box body, a PCB (printed circuit board) is arranged on the bottom plate base, and the PCB is of a single-sided circuit board structure. The surface of the PCB is provided with a plurality of surface-mounted elements, and the bottom of the PCB is provided with a long-strip-shaped bonding pad. According to the utility model, a PCB (Printed Circuit Board) and a surface-mounted element used in the existing filter structure technology are improved, so that the purposes of high reliability and light weight are achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of design and manufacture of crystal filters for communication and navigation, and more specifically, the utility model relates to a high-frequency crystal filter structure. Background Art

[0002] A filter is an important component in wireless communication, aiming to allow the required signals to pass through and exclude the unnecessary signals; a quartz crystal is a type of piezoelectric crystal. The quartz crystal is used as a time or frequency reference source in a circuit and can be regarded as the heart of the device. The quartz crystal has the piezoelectric effect. If pressure is applied to the quartz wafer, charges will be generated on the wafer; conversely, when a voltage is applied to the electrodes at both ends of the wafer, the crystal will undergo mechanical deformation. The traditional crystal filter structure is composed of multiple through-hole components, and the size and weight will be large, requiring careful design and assembly.

[0003] In recent years, the requirements for miniaturization and high reliability of aviation complete machines have been reflected in some electronic component products. Reducing the weight and volume of complete machines has also become the goal of product structure improvement for some companies. Accordingly, the quartz crystal filters supporting the complete machines have also put forward the requirement of weight reduction. In view of this situation, reducing the size and weight of filter products has become the main goal of improving the structure of new products. Content of the Utility Model

[0004] In order to overcome the above-mentioned defects of the prior art, the utility model provides a high-frequency crystal filter structure.

[0005] To achieve the above object, the utility model provides the following technical solution: a high-frequency crystal filter structure, including a box body, a bottom plate base is arranged on the lower surface inside the box body, a PCB circuit board is arranged on the bottom plate base, the PCB circuit board is of a single-sided circuit board structure, and a plurality of surface-mounted components are arranged on the surface of the PCB circuit board, and a long strip solder pad is arranged at the bottom of the PCB circuit board.

[0006] As a further improvement of the technical solution of the utility model, an upper cover is further arranged on the box body, and the upper cover and the bottom plate base are sealed with tin.

[0007] As a further improvement of the technical solution of the utility model, M3 fixing bolts are arranged on both sides of the lower surface of the bottom plate base.

[0008] As a further improvement of the technical solution of the utility model, filter electrical performance insulator pins penetrating through the inside of the bottom plate base are arranged at both ends of the bottom plate base, and via holes corresponding to the positions of the filter electrical performance insulator pins are opened at both ends of the PCB circuit board.

[0009] As a further improvement of the technical solution of the present utility model, the via pad is a through hole, and the pins of the two filter electrical property insulators are correspondingly inserted and connected to the two via pads on the PCB circuit board.

[0010] As a further improvement of the technical solution of the present utility model, the plurality of surface mount components include a patch adjustable capacitor and a patch fixed capacitor.

[0011] As a further improvement of the technical solution of the present utility model, the patch adjustable capacitor and the patch fixed capacitor are both arranged on the rear surface of the PCB circuit board. The rear surface of the PCB circuit board is also provided with a through-hole crystal resonator and an inductance coil. The through-hole crystal resonator is connected to the inductance coil, the patch adjustable capacitor, and the patch fixed capacitor through the conducting wires on the PCB circuit board.

[0012] Advantages of the present utility model:

[0013] 1. The high-frequency crystal filter structure adopts surface mount components with high reliability, small volume and light weight. As auxiliary components in the high-frequency crystal filter structure, the positions of the various mount components are reasonably selected and arranged, and shielding measures are increased to improve the anti-interference ability, ensuring that the filter is light in weight while improving the high stopband attenuation index of the filter;

[0014] 2. The PCB circuit board is used to replace the traditional metal clip structure. By controlling parameters such as the dielectric constant, temperature coefficient of the circuit board material, thickness uniformity of the copper clad laminate, and width of the copper foil on the circuit board, a highly reliable design of the filter is achieved, effectively improving the reliability of the product while reducing the weight of the filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a front schematic view of a PCB circuit board of a high-frequency crystal filter structure according to an embodiment of the present utility model;

[0016] Figure 2 is a rear schematic view of a PCB circuit board of a high-frequency crystal filter structure according to an embodiment of the present utility model;

[0017] Figure 3 is a 3D schematic view of a high-frequency crystal filter structure according to an embodiment of the present utility model;

[0018] Figure 4 is a front view of a high-frequency crystal filter structure according to an embodiment of the present utility model;

[0019] Figure 5 is a rear view of a high-frequency crystal filter structure according to an embodiment of the present utility model;

[0020] Figure 6It is a top view of a high-frequency crystal filter structure that can be selected according to an embodiment of the present invention;

[0021] Figure 7 It is a PCB circuit diagram of a high-frequency crystal filter structure that can be selected according to an embodiment of the present invention;

[0022] Figure 8 It is an external dimension diagram of a high-frequency crystal filter that can be selected according to an embodiment of the present invention.

[0023] The reference numerals are: 1, PCB circuit board; 2, through-hole crystal resonator; 3, inductance coil; 4, M3 fixing bolt; 5, bottom plate base; 6, surface mount adjustable capacitor; 7, surface mount fixed capacitor; 8, via pad; 9, long strip pad; 10, filter electrical performance insulator pin. Detailed implementation manners

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] As shown in the attached Figure 1-8 A high-frequency crystal filter structure shown, such as Figure 3 , Figure 4 Figure 5 and Figure 6 shown, includes a box body, a PCB circuit board 1, surface mount components, and a through-hole crystal resonator 2; a bottom plate base 5 is provided on the inner lower surface of the box body; the PCB circuit board 1 is a single-sided circuit board, and the PCB circuit board 1 is vertically arranged on the bottom plate base 5. The PCB circuit board 1 is made of a high-frequency dielectric board. After understanding parameters such as the dielectric constant of the circuit board material, the temperature coefficient, the thickness uniformity of the copper clad laminate, and the width of the copper foil on the circuit board, a suitable material is determined, and then the layout-rationalized layout is entrusted to a PCB circuit board manufacturer for subcontracting; the surface mount components are multiple, including 5 surface mount adjustable capacitors 6 and 5 surface mount fixed capacitors 7, and 8 through-hole crystal resonators 2 are evenly distributed on the surface of the PCB circuit board 1. Multiple surface mount components and through-hole crystal resonators 2 are all arranged on the PCB circuit board 1. The structural weight of the high-frequency crystal filter structure does not exceed 27 g, and the requirements of light weight and high performance can be achieved, solving the problem of reducing the volume and weight by using surface mount components in the existing whole-machine filter structure.

[0026] During specific implementation, such as Figure 3 , Figure 4 and Figure 5As shown, the box body is provided with an upper cover and a bottom plate base 5. The upper cover and the bottom plate base 5 are combined into a box-type high-frequency crystal filter structure by tin sealing, and both the upper cover and the bottom plate base 5 are made of brass plated with nickel.

[0027] Further, M3 fixing bolts 4 are provided on the left and right sides of the lower surface of the bottom plate base 5, and one filter electrical performance insulator pin 10 penetrating through the bottom plate base 5 is provided at each end of the bottom plate base 5 along the length direction.

[0028] Further, there are two filter electrical performance insulator pins 10. Two filter electrical performance insulator pins 10 are provided at both ends of the bottom plate base 5 along the length direction. The functions of the two filter electrical performance insulator pins 10 are respectively the input signal terminal and the output signal terminal.

[0029] During specific implementation, through-hole pads 8 corresponding to the filter electrical performance insulator pins 10 one by one are respectively provided at both ends of the PCB board 1 along the length direction.

[0030] Further, a long strip pad 9 is provided at the lower part of the surface of the PCB board 1. The PCB board 1 is placed vertically, and the PCB board 1 is fixed on the bottom plate base 5 by using the long strip pad 9 and welded to the bottom plate base to form an integral body.

[0031] Further, both of the two through-hole pads 8 are through holes, and the two filter electrical performance insulator pins 10 are respectively connected to the two through-hole pads 8 on the PCB board 1 through conductor leads.

[0032] During specific implementation, such as Figure 4 and Figure 5As shown, multiple surface-mounted components include a surface-mounted fixed capacitor 7 and a surface-mounted adjustable capacitor 6. The through-hole crystal resonator 2 is a key component in the high-frequency crystal filter structure. The theoretical parameters of each component are calculated through theoretical formulas and verified multiple times. The key electrical performance index parameters (L1, C1, C0, Fr, RR) of the through-hole crystal resonator 2 required for the high-frequency crystal filter structure are estimated, and the approximate range of the parameters of the through-hole crystal resonator 2 component is determined. A subcontractor is entrusted for design and processing. The comprehensive design of the parameters of the through-hole crystal resonator 2, such as the electrode area, wafer vibration mode, wafer return frequency, etc., is the key part of the through-hole crystal resonator 2. The relevant parameters of the finally determined through-hole crystal resonator 2 are shown in Table 1; the external dimensions of the surface-mounted adjustable capacitor 6 are 3.2×4.5×1.6 mm. The stator with color coding on the surface is convenient for identifying the capacitor to avoid errors during installation. It is specifically designed for surface-mounted PCB circuit board devices. The material of heat-resistant resin can withstand the high temperature of reflow soldering. A conventional debugging tool with a thickness of 0.5 mm is used for adjustment; the inductance coil 3 uses a toroidal core of model NX0-60 with dimensions of 5 mm×2.5 mm×1.5 mm. The wire wound can be thicker to enhance the mechanical holding effect, and silicone can be used for fixation to prevent loosening; to ensure that the inductance coil 3 has the least impact on the high-frequency circuit, it is necessary to keep the parameters of each arm of the filter consistent. The inductance values connected in series on the series arm and parallel arm crystal resonators should be as consistent as possible. The more the resonance frequency changes, the larger the inductance required in series. Along with the increase of the series inductance, the distributed capacitance will increase, and the influence of the inductance element on the crystal filter circuit will be obvious. The inductance value of the spreading inductance should not be too large.

[0033] Table 1 Relevant Parameters of Through-Hole Crystal Resonator

[0034] Furthermore, the surface-mounted fixed capacitor 7 and the surface-mounted adjustable capacitor 6 are arranged in front of the PCB circuit board 1, and the through-hole crystal resonator 2 and the inductance coil 3 are arranged behind the PCB circuit board 1. They are fixed by soldering through the pads on the surface of the PCB circuit board 1. The through-hole crystal resonator 2 is connected to the surface-mounted fixed capacitor 7, the surface-mounted adjustable capacitor 6, and the inductance coil 3 through the layout lines on the surface of the PCB circuit board 1.

[0035] In specific use of this embodiment, first, the PCB circuit board 1 is vertically welded to the bottom board base 5 to fix the PCB circuit board 1 on the bottom board base 5. Then, the through-hole crystal resonator 2, the surface-mounted fixed capacitor 7, and the surface-mounted adjustable capacitor 6 are respectively surface-mounted and welded to the surface of the PCB circuit board 1. The inductor coil 3 is welded to the corresponding pads and lead ports of the PCB circuit board 1. Then, the two via pads 8 of the PCB circuit board 1 are welded to the leads inside the pins 10 of the two filter electrical property insulators on the bottom board along the horizontal direction from front to back by conductor leads. Then, a certain shielding structure is used to separate each crystal resonator unit. At the same time, the inductor coil 3 is wrapped with a special structure to meet the requirements of high attenuation in the stopband of the high-frequency filter. Finally, the upper cover is installed to form the product to be sealed. The sealed product is encapsulated by tin sealing. Preheat a 75W soldering iron for 20 minutes. Dip a little flux with a No. 7 oil painting brush and apply it to the encapsulation part of the filter. When the welding temperature reaches 380°C - 400°C, use the soldering iron to evenly seal along the bottom edge joint of the high-frequency crystal filter. Weld each side in one direction at a time, and the welding time does not exceed 5 seconds. The width of the welded surface is about 3mm. It is required that the welding is flat, smooth, without solder accumulation, burrs, air gaps, or false soldering. Finally, use straight tweezers to hold a cotton ball to wipe alcohol to remove the residual rosin and oxide traces at the sealed part. Then, wipe the entire high-frequency crystal filter box body with a clean alcohol cotton ball and dry it with a cotton cloth to make the appearance of the high-frequency crystal filter neat and beautiful. After passing the sealed inspection, it is sent to the next process. Through sampling inspection of a batch of high-frequency crystal filters with this structure, using a network analyzer and an electronic scale, the electrical performance attenuation index and weight of the product are tested. The test environment temperature is 25.6°C, and the environmental humidity is 36%RH. The test data is shown in Table 2 below. From the data in the table, it can be seen that the average weight of the high-frequency crystal filter with this structure is reduced by 15% compared with 32g of the internal metal clip structure, realizing the reliable structural design of the high-frequency crystal filter and achieving the purpose of good stopband attenuation characteristics and weight reduction.

[0036] Table 2 Height and Weight Test Data

[0037] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-frequency crystal filter structure, comprising a box body, characterized in that: A bottom plate base (5) is provided on the inner lower surface of the box body, a PCB circuit board (1) is provided on the bottom plate base (5), the PCB circuit board (1) is of a single-sided circuit board structure, and a plurality of surface-mounted components are provided on the surface of the PCB circuit board (1), and a long strip pad (9) is provided at the bottom of the PCB circuit board (1).

2. The high-frequency crystal filter structure according to claim 1, characterized in that: An upper cover is further provided on the box body, and the upper cover and the bottom plate base (5) are sealed with tin.

3. The high-frequency crystal filter structure according to claim 1, characterized in that: M3 fixing bolts (4) are provided on both sides of the lower surface of the bottom plate base (5).

4. The high-frequency crystal filter structure according to claim 1, wherein: Filter electrical performance insulator pins (10) penetrating through the inside of the bottom plate base (5) are provided at both ends of the bottom plate base (5), and via pads (8) corresponding to the positions of the filter electrical performance insulator pins (10) are provided at both ends of the PCB circuit board (1).

5. The high-frequency crystal filter structure according to claim 4, characterized in that: The via pads (8) are through holes, and two filter electrical performance insulator pins (10) are correspondingly inserted and connected to the two via pads (8) of the PCB circuit board (1).

6. The high-frequency crystal filter structure according to claim 1, wherein: The plurality of surface-mounted components include a patch adjustable capacitor (6) and a patch fixed capacitor (7).

7. The high-frequency crystal filter structure according to claim 6, wherein: The patch adjustable capacitor (6) and the patch fixed capacitor (7) are both provided on the rear surface of the PCB circuit board (1), and a through-hole crystal resonator (2) and an inductor coil (3) are further provided on the rear surface of the PCB circuit board (1), and the through-hole crystal resonator (2) is connected to the inductor coil (3), the patch adjustable capacitor (6) and the patch fixed capacitor (7) through lead wires on the PCB circuit board (1).

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